Basic telecom
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Basic telecom Basic telecom Presentation Transcript

  • Basic Telecom It’s all about signaling Samuel Dratwa Samuel.dratwa@gmail.comCopyright © 2011 LOGTEL
  • What are we selling ? customer satisfaction ! It’s all about customer satisfactionCopyright © 2011 LOGTEL
  • Course Content 1. Introduction • What is telecom ? 2. Telephony history – form Bell to analog switch 3. Telecom Network • Switching • telecom services 4. Moving to Digital 5. Basic Signaling (SS7) 6. ISP / Data network 7. Mobile 3Copyright © 2011 LOGTEL
  • Goals • To understand the terminology • To know where did we come from • To understand the need and the various signalingCopyright © 2011 LOGTEL 4
  • What is Telecom ? Telecommunication is the transmission of information over significant distances to communicate. Signaling: the information exchange concerning the establishment and control of a telecommunication circuit and the management of the network, in contrast to user information transferCopyright © 2011 LOGTEL 5
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  • Switching Systems  Manual control—Switch/cord boards Off-Hook Indicator Tip Ring Patch Cord PairsManual RingCopyright © 2011 LOGTEL
  • The Telephone: Tip and RingCopyright © 2011 LOGTEL
  • Strowger switch (Step by Step) - 1891Copyright © 2011 LOGTEL 9
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  • Signaling – E&M (Ear and Mouth) inbound • On-hook • Off-hook • Line tone • Dialing • Ringing • Ring back tone • Busy toneCopyright © 2011 LOGTEL 12
  • Setup of a PSTN call (meet Alice and Bob) Alice Exchange A Exchange B Bob off-hook dial tone Bob number ringing tone ringing tone Bob answers connection okCopyright © 2011 LOGTEL
  • Crossbar – 1920’s to 80’s Now we can invent DTMF and now we can have logic (!)Copyright © 2011 LOGTEL 14
  • Tone Dialing Dual Tone Multifrequency (DTMF) 1209 1336 1477 1633 697 1 2 3 A Timing: 770 4 5 6 B 60 ms Break 40 ms Make 852 7 8 9 C 941 * 0 # DCopyright © 2011 LOGTEL
  • Copyright © 2011 LOGTEL
  • N11 code  2-1-1: community services, United Way  3-1-1: municipal government services, non-emergency  4-1-1: directory assistance  5-1-1: traffic information or police non-emergency services  6-1-1: telephone company customer service and repair  7-1-1: TDD relay for the deaf  8-1-1: underground public utility location,[1] in Canada 8- 1-1 is assigned for non-emergency health information and services  9-1-1: emergency servicesCopyright © 2011 LOGTEL 17
  • Telecom Network Elements Core network  SDH – Synchronous Digital Hierarchy (Europe)  SONET – Synchronous optical networking (USA) Switches  Class 4 – network services  Class 5 – Line services Signaling  IN – Intelligent Network  SS7 – (Common Channel) Signaling System #7  SIP – Session Initiation Protocol Access / Last mile  Twisted per  FTTx – fiber to the X  WirelessCopyright © 2011 LOGTEL
  • Telecom Management – OSS/BSS Traditional definitions OSS BSS• Network facing operational • Customer facing business support systems support systems• Run by Network Operations • Run by the IT department• Typically including service • Typically including billing and activation, provisioning, fault CRM management, etc • Revenue-focused• Cost-focusedCopyright © 2011 LOGTEL 19
  • eTOM – NGOSS - FrameWorXCopyright © 2011 LOGTEL
  • Classes 1-5Copyright © 2011 LOGTEL
  • CLASS (Custom Local Area Signaling Services)• AKA VSC (vertical service code) - developed by AT&T in the 1960s• a special code dialed prior to (or instead of) a telephone number that engages some type of special telephone service • Anonymous Call Rejection: start • Anonymous Call Rejection: cancel • Busy Number Redial : start • Busy Number Redial : cancel • Call Forwarding: start • Call Forwarding: cancel • Call Return (incoming) • Call Waiting disable • Caller ID DisableCopyright © 2011 LOGTEL 22
  • MDF - Main Distribution FrameCopyright © 2011 LOGTEL
  • MOVING TO DIGITALCopyright © 2011 LOGTEL
  • Trunks to SDH A trunk line is a circuit connecting telephone switchboards (local loop circuit which extends from telephone exchange switching equipment to individual telephones)• DS0 (Digital Signal 0) / T0 / E0 – 64Kb/s Nyquist rate• DS1 / T1 – 1.5Mb/s E1 – 2Mb/s• DS3 / T3 - Copyright © 2011 LOGTEL 25
  • Why 3.4 KHz ? Bandpass Filtering Signal Energy Distribution for Human Speech 0 Hz 300 Hz 3,400 Hz 20 kHz Bandwidth (3.1 kHz) The human ear can hear sounds up to 20 kHz, but most sound is between 300 Hz and 3.4 kHz. The bandpass filter only passes this sound to reduce bandwidth. 26Copyright © 2011 LOGTEL
  • Time Division Multiplexing (TDM) Time Frame 1 Frame 2 Frame 3 Used Used Used Used Used Slot 1 Slot 1 Slot 1 for for for Circuit A Slot 2 Circuit A Circuit A for Circuit B Slot 3 TDM reserves capacity for for each circuit in each frame; Circuit C assures speed but is wastefulCopyright © 2011 LOGTEL 27
  • SONET and SDH  Synchronous Optical Network (SONET)  High-speed, fiber optic networks organized in rings  Synchronous Digital Hierarchy (SDH)  Fiber ring networks used internationally  Essentially the same as SONETCopyright © 2011 LOGTEL
  • SONET and SDH (contd)The basic measure of SONET speed is the Synchronous Transport Signallevel 1 (STS-1) frame, which travels at51.84 MbpsCopyright © 2011 LOGTEL
  • SONET and SDH (contd)The basic unit for SDH is the Synchronous Transport Module(STM)-1 frame, which travels at 155.52 MbpsCopyright © 2011 LOGTEL
  • SONET and SDH (contd)Benefits of using SONET/SDH You can use multiplexors and routers to combine different data lines and streams onto one line One heterogeneous network can communicate with another distant heterogeneous network via one fiber optic ringCopyright © 2011 LOGTEL
  • SDH Rings 34 Mb/s 2 Mb/sCopyright © 2011 LOGTEL 32
  • Introducing ISDN  Telephone companies developed ISDN (Integrated Services Digital Network) as part of an effort to standardize subscriber services.  This included the User-Network Interface (UNI), better known as the local loop.  The ISDN standards define the hardware and call setup schemes for end-to-end digital connectivity.  These standards help achieve the goal of worldwide connectivity by ensuring that ISDN networks easily communicate with one another.  In an ISDN network, the digitizing function is done at the user site rather than the telephone company.Copyright © 2011 LOGTEL Rick Graziani 33
  • ISDN Advantages  ISDN also provides more bandwidth than a traditional 56 kbps dialup connection.  ISDN uses bearer channels, also called B channels, as clear data paths.  Each B channel provides 64 kbps of bandwidth.  An ISDN connection with two B channels would provide a total usable bandwidth of 128 kbps.  Each ISDN B channel can make a separate serial connection to any other site in the ISDN network.  ISDN lines can be used in conjunction with PPP encapsulation.Copyright © 2011 LOGTEL Rick Graziani 34
  • Signaling Categories Signaling categories:  Supervision – detects changes to a particular line  Addressing – responsible for routing signals to the correct switch  Alerting – audible alert signals  Call progress – signals that maintain calls Audible call progress tones:  Dial tone  Busy signal  Receiver off hook too long  Nonexistent numberCopyright © 2011 LOGTEL
  • In-Band and Out-of-Band Signaling  In-band signaling  The process of allowing the control signal to share the same path as the voice and data  AKA CAS (Channel Associated Signaling)  Out-of-band signaling  The process of using a separate channel for signaling purposes  AKA CCS (Common Channel Signaling)Copyright © 2011 LOGTEL
  • Advantage of CCS over CAS• Faster call setup• No interference between signaling tones by network and frequency of human speech pattern.• Greater Trunking Efficiency: CCS has shorter call set up and tear down times that result in less call holding time, thereby reducing the traffic on the network.• Information Transfer: CCS allows the transfer of additional information along with the signaling traffic providing facilities such as caller identification and voice or data identificationCopyright © 2011 LOGTEL
  • SS7 – Signaling System #7 (80’s) SS7 network major components include:  SSP (Service Switching Point)  STP (Signaling Transfer Point)  SCP (Service Control Point)  SL (signaling link)Copyright © 2011 LOGTEL
  • SSP (Service Switching Point) • SSP is the local exchange to the subscriber and the interface to the telephone network. • The SS7 signaling information is produced at the sending SSP and is handled at the receiving SSP. • It converts voice (in band) signaling into the SS7 signal units (out band), and vice versa.Copyright © 2011 LOGTEL
  • STP (Signaling Transfer Point)• STP is the network node.• It works like a router to perform the routing of messages to other signaling points.• It is usually paired to provide redundancy for a reliable message transfer.• It is adjunct to a voice switch, and might stand alone as a separate machine. (It’s the tandem in class 4/4)Copyright © 2011 LOGTEL
  • SCP (Service Control Point)• SCP works as the interface with the databases, which contain the information of the subscribers, such as 800 service, calling cards, fraud data, etc.• When receiving a request, it is triggered to handle the database queries, and returns a response with the results of the queries to the originating SSP.Copyright © 2011 LOGTEL
  • Basic Architecture of a IN SMS SMS – Service Management System SCP – Service Control Point STP – Service Transfer Point SCP SSP – Service Switching Point SS7 STP STP IP SSP SSPIP – Intelligent Peripheral IP Formats in INs Slide 42 Copyright © 2011 LOGTEL
  • Basic Call Setup Example• Initial address message (IAM): contains all necessary information for a switch to establish a connection• Address complete message (ACM): acknowledge to IAM; the required circuit is reserved and the ―phone is ringing‖ (ring back tone)• Answer message (ANM): occurs when the called party picks up the phone• Release (REL): sent by the switch sensing that the phone hung up• Release complete (RLC): each exchange that receives REL, sends an RLC message back (this acknowledges receipt of REL) 6,10 2 1 5 1 9 3 Copyright © 2011 LOGTEL
  • Setup of a call using ISUP Alice Exchange A Transit exchange Exchange B Bob Setup IAM IAM Setup Q.931 Link-by-link routing (number analysis) Alert ACM ACM Alert Connect ANM ANM Connect Link-by-link signalling (no number analysis) Charging of call starts nowCopyright © 2011 LOGTEL
  • Some basic ISUP messages user A user B IAM – Initial Address Message ACM – Address Complete Message ANM – Answer Message REL – Release Message RLC – Release CompleteCopyright © 2011 LOGTEL
  • Intelligence Network (90’s) Before IN?  All services were to be implemented directly in the core switch systems.  Contact Vendors: Headache for service providers. What actually is IN?  An architecture that redistributes a portion of the call processing, that is traditionally performed by tel-switches, to other nodes. Two types of IN today:  Intelligence Network (IN) – standardized by ITU.  Advanced Intelligent Network (AIN) - standardized by Bellcore.Copyright © 2011 LOGTEL
  • Why Intelligent Networking? Introduce new services rapidly: IN provides the capability to provision new services or modify existing services throughout the network with physical intervention. Provide Service Customization: Service providers require the ability to change the service logic rapidly and efficiently. Customers are also demanding control of their own services to meet their individual needs. Establish Vendor Independence: To develop the software for service providers quickly and efficiently, suppliers have to integrate commercially available software to create the applications required by service providers. Create open interfaces: Open interfaces allow service providers to introduce network elements quickly for individualized customer services. Capable to act appropriately in a changing environmentCopyright © 2011 LOGTEL
  • IN service family 1. Number translating 2. Billing modification  Reverse charging (800)  Split charging (700) in mobile networks IN CAMEL  Premium rate (900) (Customised Applications for  Personal services (600) Mobile networks Enhanced 3. Centralize Voice Mail Logic) 4. Pre Paid (node) 5. SMS – Short MassagingCopyright © 2011 LOGTEL 48
  • Centrex • Centrex is a PBX-like service providing switching at the central office instead of at the customers premises. Typically, the telephone company owns and manages all the communications equipment and software necessary to implement the Centrex service and then sells various services to the customer. • Today we use the terms:  Hosted  Stickiness  Virtual  CloudCopyright © 2011 LOGTEL 49
  • PABX (voice) Services (1) Private (automatic) Branch eXchange • Auto attendant • Automatic call distributor • Automated directory services (where callers can be routed to a given employee by keying or speaking the letters of the employees name) • Call accounting • Call blocking • Call forwarding on busy or absence • Call park • Call pick-up • Call transfer • Conference call • Custom greetings • Busy OverrideCopyright © 2011 LOGTEL 50
  • PABX service (2) • Direct Inward Dialing (DID) – AKA DDI and DDO • Direct Inward System Access (DISA) (the ability to access internal features from an outside telephone line) • Do not disturb (DND) • Follow-me, also known as find-me: Determines the routing of incoming calls. The exchange is configured with a list of numbers for a person. When a call is received for that person, the exchange routes it to each number on the list in turn until either the call is answered or the list is exhausted (at which point the call may be routed to a voice mail system). • Interactive voice response • Music on hold • Night serviceCopyright © 2011 LOGTEL 51
  • Signaling in VoIP networksVoIP Network can carry SS7 over IP using protocols definedby Signaling Transport (SIGTRAN).Copyright © 2011 LOGTEL
  • DATA NETWORKINGCopyright © 2011 LOGTEL
  • OSI 7 Layer Model Application  OSI - Open Systems Interconnection (Basic Presentation Reference Model)  Each level is an independent Session set of protocols  Each level can be change Transport seamlessly Network Data Link PhysicalCopyright © 2011 LOGTEL
  • 5 Layer model Application Presentation Application Session Transport Transport Network Network Data Link Data Link Physical PhysicalCopyright © 2011 LOGTEL
  • 5 Layer model (TCP/IP)  Application – Represent the end user and the application he Application use (mail, browse, FTP, etc.)  Transport - end-to-end message transfer, along with error control, fragmentation and flow control.  Network (AKA Internet) – Transport - TCP responsible on getting packets of data from source to Network - IP destination.  Link - processes of Link transmitting receiving packets on a given link layerCopyright © 2011 LOGTEL
  • TCP/IP ConnectionCopyright © 2011 LOGTEL
  • TCP - Transmission Control Protocol  Connection oriented - Reliable stream transport  Conceptually, two ends communicate to agree on details  After agreeing application notified of connection  During transfer, ends communicate continuously to verify data received correctly  When done, ends tear down the connection  Provides buffering and flow control  Takes care of lost packets, out of order, duplicates, long delays  Usually used for browsing, FTP, Mail, etc.Copyright © 2011 LOGTEL
  • Web server Samuel Browser Web Site read(s1, dataBlock) send(s2, dataBlock) Transport (TCP) Transport (TCP) Router 1 2 3 4 5 1 2 3 4 5 Network (IP) Network (IP) Network (IP) 1 2 3 4 5 1 2 3 1 2 3 4 5 Link (WLAN) Link Link (WLAN) 1 2 3 4 5 1 2 3 1 2 3 4 5 Physical Physical PhysicalCopyright © 2011 LOGTEL
  • UDP- User Datagram Protocol  Connectionless Datagram- Not Reliable transport  Minimal overhead, high performance  No setup/teardown, 1 datagram at a time  Application responsible for reliability  Includes datagram loss, duplication, delay, out-of-sequence, multiplexing, loss of connectivity  Usually used for Voice & Video streaming, broadcasting, etc.Copyright © 2011 LOGTEL
  • TCP vs. UDP data format 0 4 8 16 24 31 Source port Destination port 0 8 16 24 31 Sequence number Source port Destination port Acknowledgement number UDP message len Checksum (opt.) Hlen Resv Code Window Data Checksum Urgent ptr … Options (if any) Padding Data if any …Copyright © 2011 LOGTEL
  • TCP data format  Port - TCP port numbers to ID applications at both ends of connection  Sequence number - ID position in sender’s byte stream  Acknowledgement - identifies the number of the byte the sender of this segment expects to receive next  Hlen - specifies the length of the segment header in 32 bit multiples. If there are no options, the Hlen = 5 (20 bytes)  Code - used to determine segment purpose, e.g. SYN, ACK, FIN, URGCopyright © 2011 LOGTEL
  • TCP data format (cont.)  Window - Advertises how much data this station is willing to accept. Can depend on buffer space remaining.  Checksum -Verifies the integrity of the TCP header and data. It is mandatory.  Urgent pointer - used with the URG flag to indicate where the urgent data starts in the data stream. Typically used with a file transfer abort during FTP or when pressing an interrupt key in telnet.  Options -used for window scaling, SACK, timestamps, maximum segment size etc.Copyright © 2011 LOGTEL
  • IP Address  Unique addresses in the world  An IP address is 32 bits, noted in dotted decimal notation:  Host and Prefix Part  An IP address has a prefix and a host part:  prefix:host  Prefix identifies a subnetwork  used for locating a subnetwork – routing  Prefix is usually identified in a host using a ―subnet mask‖Copyright © 2011 LOGTEL
  • Using a mask: address + mask  the mask is the dotted decimal representation of the string made of : 1 in the prefix, 0 elsewhere  bit wise address & mask gives the prefix  example 1: mask  here: prefix is  example 2: mask  Q1: what is the prefix ?  Q2: how many host ids can be allocated ?Copyright © 2011 LOGTEL
  • Address + Mask (example 2)  mask ▪ Q1: what is the prefix ? A: 129 132 119 77 1000 0001 1000 0100 0111 0111 0100 1101 255 255 255 192 64 addresses 1111 1111 1111 1111 1111 1111 1100 0000 26 6 129 132 119 64 1000 0001 1000 0100 0111 0111 0100 0000 Q2: how many host ids can be allocated ? ▪ A: 64 (minus the reserved addresses: 62)Copyright © 2011 LOGTEL
  • IP V.6 vs. V.4 DatagramCopyright © 2011 LOGTEL
  • IP v.4 header  Version (4 bits) – 6 or 4  Hlen (4 bits) - Header length in 32 bit words, without options (usual case) = 20  Type of Service (TOS 8 bits): now being used for QoS  Total length (16 bits) - length of datagram in bytes, includes header and data  Time to live (TTL 8bits) - specifies how long datagram is allowed to remain in internet (how many hops)  Protocol (8 bits) - specifies the format of the data area  Protocol numbers administered by central authority to guarantee agreement, e.g. TCP=6, UDP=17 …Copyright © 2011 LOGTEL
  • IP v.6 header  Version (4 bits) – 6 or 4  Traffic Class (8 bits) - traffic priority delivery value.  Flow Label. 20 bits. Used for specifying special router handling from source to destination(s) for a sequence of packets.  Payload Length (16 bits) - Specifies the length of the data  Hop Limit (8 bits) - the same as TTL in the IPv4  Source address. 16 bytes.  Destination address. 16 bytes.Copyright © 2011 LOGTEL
  • IPv6 address – 128 bit  IPv6 address is made of two parts: prefix and suffix (I.e interface-ids) 64 bits 64 bits prefix suffix and hierarchical structure (that depends on format prefix, FP)  prefix: FP TLA NLA SLA FP – Format prefix TLA - Top-Level Aggregators  suffix: NLA - Next-Level Aggregators Interface ID SLA – Service level Agreements  Link-local address (mandatory) is unique within a "link". 1111111010 54 0 64 bits bits suffixCopyright © 2011 LOGTEL
  • IPv6 Autoconfiguration and Renumbering  RFC 2462, IPv6 Stateless Address Autoconfiguration.  IPv6 includes stateless address autoconfiguration feature, which allows a host to determine its own IPv6 address from its Layer 2 address.  The concept: A device generates a temporary address until it can determine the characteristics of the network it is on. Then creates a permanent address it can use based on that information.  In the case of multi-homed devices: Autoconfiguration is performed for each interface separately Stateless address Stateful address autoconfiguration autoconfiguration No central server needed to aid in address Central server allocates full addresses configuration to nodes on request Node forms its own suffix, checks if it is DHCPv6 is the current protocol for unique stateful address autoconfiguration Node obtains prefix(es) from the nearest routerCopyright © 2011 LOGTEL
  • IPv6 Extended Unique Identifier (EUI-64)  RFC 2464  IPv6 link-local addresses and statelessly autoconfigured addresses on Ethernet networks  used in Router Solicitation, Router Advertisement, Neighbor Solicitation, Neighbor Advertisement and Redirect messages 48-bit MAC address 64-bit IPv6 EUICopyright © 2011 LOGTEL
  • IPv6 address Types Unicast (1:1) communicate specified one computer Anycast addresses :  nearest node of a set of nodes RFC 4291 currently specifies the following restrictions on anycast addresses: An anycast address must not be used as the source address of a packet. Any anycast address can only be assigned to a router  currently only used to address routers  Multicast (1:n) communicate group of computers No more broadcast in useCopyright © 2011 LOGTEL
  • Representation of IPv6 addresses  Colon hexadecimal notation - 805B:2D9D:DC28:0000:0000:FC57:D4C8:1FFF  Leading zeroes can be suppressed in the notation 805B:2D9D:DC28:0:0:FC57:D4C8:1FFF  Zero Compression in IPv6 Addresses 805B:2D9D:DC28::FC57:D4C8:1FFF  The double-colon can appear only once in any IP address.  IPv6 addresses can embed IPv4. The notation has the first 96 bits in colon hex notation, and the last 32 bits in dotted decimal. eg ::  Prefix notation can be used as with classless IPv4 addressing with CIDR. Example: 805B:2D9D:DC28::FC57:D4C8:1FFF/48Copyright © 2011 LOGTEL
  • So why isn’t it here yet ?  No clear move to IPv6  Lack of smooth migration plans  Investments in IPv4  Software availability - Available from Microsoft Windows XP sp2  Developments in IP v4  Use of NAT  CIDR  Planning of Hierarchies and use of Autonomous Areas  IPsec implemented in IPv4  Other Points  Router Upgrades to handle IPv6 – OSPFv3Copyright © 2011 LOGTEL
  • Tunneling IPv6 over IPv4 Transport IPv6 Header Data Header IPv6 Dual-Stack Dual-Stack IPv6 Host Router Router Host IPv6 IPv4 IPv6 Network Network Tunnel: IPv6 in IPv4 packet Transport IPv4 Header IPv6 Header Data Header  IPv6 can operate within a closed or private network environment  Currently across a public networks, such as the Internet, have to cross an IPv4 domain  IPv6 packets can be encapsulated within IPv4  Encapsulated packets can then travel transparently across an IPv4 routing domain  Tunneling can be used by routers and hostsCopyright © 2011 LOGTEL
  • MOBILE NETWORKSCopyright © 2011 LOGTEL
  • Cellular Technology Defined: A communications system which serves users via radiowaves (a “radio air interface”) by connecting the user’s mobileterminal to the antennas at the nearest “cell base station”.The cell base station antennas can be tower mounted; rooftopmounted; mounted on water tanks; or hidden from sight foraesthetic purposes. Average base station coverage areatoday: 2-5 miles radius. The system functions by re-using frequencies at the low-powered cell base stations throughout a cellular marketarea, and handing off calls in progress from one cell basestation to another as users move throughout the market area.Copyright © 2011 LOGTEL
  • Course Content 1. Introduction • What is telecom ? 2. Telephony history – form Bell to analog switch 3. Telecom Network • Switching • telecom services 4. Moving to Digital 5. Basic Signaling (SS7) 6. ISP / Data network 7. Mobile 7 9Copyright © 2011 LOGTEL
  • Telecom Network Elements Core network  SDH – Synchronous Digital Hierarchy (Europe)  SONET – Synchronous optical networking (USA) Switches  Class 4 – network services  Class 5 – Line services Signaling  IN – Intelligent Network  SS7 – (Common Channel) Signaling System #7  SIP – Session Initiation Protocol Access / Last mile  Twisted per  FTTx – fiber to the X  WirelessCopyright © 2011 LOGTEL
  • Call BaseStation PhotosCopyright © 2011 LOGTEL
  • Stealth Cell SitesCopyright © 2011 LOGTEL
  • Mobile Telephone (Cellular Technology)  Wireless service is founded on one key concept known as ―frequency re-use‖  Cellular service launched in Chicago in 1983  Traditionally, to engineer a cell network to support millions of users in a metropolitan area, or thousands in a rural area, markets are broken down into cells. Cells are geographic areas that use their own sets of frequencies (channels) to support dozens of users simultaneously.  Frequency re-use is accomplished by breaking down all available frequencies into groups of 7 (N=7).  Each cell base station has its own transmission system (antennas) and set of assignable channels.Copyright © 2011 LOGTEL
  • N=7 Frequency Re-Use Cluster. Each hexagon represents a base station with distinct set of frequencies. Note how identical frequency sets are laid out symmetrically. This facilitates design and engineering.Copyright © 2011 LOGTEL
  • Two Antenna Types: Omnidirectional: propagates radio signal equally 360 degrees, aka ―omni‖. Also called ―stick‖ antennas. (Lamp With No Shade) Directional: radio energy is focused in a specific direction at a specific beamwidth, based on a reflector within the antenna housing. (Flashlight)Copyright © 2011 LOGTEL
  • Five Key Components To Every (Macro) Wireless Network:  Mobile phone, aka ―UE‖ (user equipment) or ―mobile terminal‖  Cell Base Station  Fixed network, AKA ―backhaul network‖  Mobile Switching Center (MSC)  Interconnection to PSTN and InternetCopyright © 2011 LOGTEL
  • MS (Mobile Station) MS BTS BSS (Base Station System) BSC PSTN, ISDN... MSC (Network Switching NSS Voicemail Server Subsystem) SM-SC VLR HLR AuC EIR OMC OMC OMM (Operations & Maintenance NMC GSM interfaces Management) X.25 linksCopyright © 2011 LOGTEL
  • Key design and engineering concepts that drive cellular technology:  Frequency Re-Use – supports simultaneous use of hundreds or thousands of frequencies (channels) to exponentially increase system capacity  Call Handoffs – seamless transfer of a call / transmission in progress from one base station to an adjacent (neighbor) base station  Frequency Agility: in handsets / terminals – ability of cell phones to operate on any one of dozens or hundreds of possible frequencies. Call handoff cannot occur without this ability. Working together, these concepts support basic cellular operation.Copyright © 2011 LOGTEL
  • Generations Of Wireless  Wireless Service(s)  Cellular service first launched in 1983 in Chicago, Illinois by Illinois Bell.  First generation (1G) service:  All analog, more prone to noise, crosstalk, call drops  Limited system capacity  Used 850 Mhz frequency spectrum  1983 – 1994  KEY DIFFERENTIATOR: first instance of frequency re-use to exponentially increase capacity over previous mobile systems  Second generation (2G) service:  Also known as ―PCS‖ (Personal Communication Service)  Co-existed with analog service for 15 years  Used different frequency spectrum (1900 Mhz / 1.9 Ghz)  KEY DIFFERENTIATOR: all digital serviceCopyright © 2011 LOGTEL
  • Generations Of Wireless  Wireless Service(s) Continued:  Third generation (3G) service:  All digital  ―Always On‖ Internet access  High-speed access and transmission (> 384 Kbps)  Technologies: UMTS (GSM-based), CDMA 1X-EVDO  KEY DIFFERENTIATOR: supports sustainable multimedia transmissions (i.e. voice, video, text, image, video)  Fourth generation (4G)  Launching in 2009 with Clearwire WiMax launch  Key technologies: WiMax (802.16) and LTE (Long Term Evolution)  KEY DIFFERENTIATOR: super-fast access and transmissions – tens of Megabits. Technology built into laptops.Copyright © 2011 LOGTEL
  • Major Challenges : – 1983 – Present: The “NIMBY” phenomenon. “Not In My Backyard”. Wireless subscribers desire – demand – great cellular coverage but protest when base station towers are installed in areas where “ugly towers” are not desired. – 2006 – Present: Backhaul network congestion and bottlenecking due to proliferation and popularity of wireless data technologies and services, based on 3G rollouts. • Traditionally, base station-to-MSC (switch) connections have been one or two DS-1 circuits. This traditional model is quickly becoming outmoded as the backhaul network now has huge potential to become a bottleneck. Adding more and more DS-1 circuits becomes expensive. Solution? Ethernet in the backhaul network: simple, known technology. Ultimately less expensive than multiple DS-1 circuits. – 2010: Radio spectrum is becoming a precious and increasingly scarce commodity. Also, data traffic vs. revenue dichotomy.Copyright © 2011 LOGTEL
  • FEATURES OF GSM (1) INCREASED CAPACITY • number of cells in the reuse patteThe GSM system provides a greater subscriber capacity than analogue systems. • GSM allows 25 kHz per user, that is, eight conversations per 200 kHz channel pair (a pair comprising one transmit channel and one receive channel). • Digital channel coding and the modulation used makes the signal resistant to interference from cells where the same frequencies are re- used (co-channel interference); a Carrier to Interference Ratio (C/I) level of 12 dB is achieved, as opposed to the 18 dB typical with analogue cellular. • This allows increased geographic reuse by permitting a reduction in the rn.Copyright © 2011 LOGTEL
  • FEATURES OF GSM (2) AUDIO QUALITY • Digital transmission of speech and high performance digital signal processors provide good quality speech transmission. • Since GSM is a digital technology, the signals passed over a digital air interface can be protected against errors by using better error detection and correction techniques. • In regions of interference or noise-limited operation the speech quality is noticeably better than analogue. USE OF STANDARDISED OPEN INTERFACES • Standard interfaces such as C7 and X25 are used throughout the system. Hence different manufacturers can be selected for different parts of the PLMN. • There is a high flexibility in where the Network components are situated.Copyright © 2011 LOGTEL
  • FEATURES OF GSM (3) IMPROVED SECURITY AND CONFIDENTIALITY • GSM offers high speech and data confidentiality. • Subscriber authentication can be performed by the system to check if a subscriber is a valid subscriber or not. • The GSM system provides for high degree of confidentiality for the subscriber. Calls are encoded and ciphered when sent over air. • The mobile equipment can be identified independently from the mobile subscriber. The mobile has a identity number hard coded into it when it is manufactured. This number is stored in a standard database and whenever a call is made the equipment can be checked to see if it has been reported stolen.Copyright © 2011 LOGTEL
  • FEATURES OF GSM (4) CLEANER HANDOVERS • GSM uses Mobile assisted handover technique. • The mobile itself carries out the signal strength and quality measurement of its server and signal strength measurement of its neighbors. • This data is passed on the Network which then uses sophisticated algorithms to determine the need of handover. SUBSCRIBER IDENTIFICATION • In a GSM system the mobile station and the subscriber are identified separately. • The subscriber is identified by means of a smart card known as a SIM. • This enables the subscriber to use different mobile equipment while retaining the same subscriber number.Copyright © 2011 LOGTEL
  • GSM Voice and Data Call Architecture Voice Calls Path Data Calls Path Packet DataCopyright © 2011 LOGTEL
  • NETWORK COMPONENTS AUC HLR  MS Mobile Station = phone + SIM card BSC  BTS Base Transceiver Station  BSC Base Station Controller  HLR Home Location Register  MSC Mobile services Switching Centre  VLR Visitor Location Register  AUC Authentication Centre VMS EIR Stand-alone or integrated in HLR  EIR Equipment Identity Register For blacklisting stolen and unwanted equipment PrePaid MSC/VLR SMSC  SMSC Short Message Service ”Support” Node Centre  VMS Voice Messaging System  PrePaid Node Hosting prepaid service system  IN Intelligent Network services INTERNET IN  PSTN Public Switched Telephone Network  PABX Private Automatic Branch Exchange MSC PSTN Mobilink w BSCCopyright © 2011 LOGTEL
  • Mobile Switching Centre (MSC) • The Mobile services Switching Centre (MSC) co-ordinates the setting up of calls to and from GSM users. • It is the telephone switching office for MS originated or terminated traffic and provides the appropriate bearer services, teleservices and supplementary services. • It controls a number of Base Station Sites (BSSs) within a specified geographical coverage area and gives the radio subsystem access to the subscriber and equipment databases. • The MSC carries out several different functions depending on its position in the network. • When the MSC provides the interface between PSTN and the BSS in the GSM network it is called the Gateway MSC. • Some important functions carried out by MSC are Call processing including control of data/voice call setup, inter BSS & inter MSC handovers, control of mobility management, Operation & maintenance support including database management, traffic metering and man machine interface & managing the interface between GSM & PSTN N/W.Copyright © 2011 LOGTEL
  • MS & ME Mobile Station (MS) The Mobile Station consists of the Mobile Equipment (ME) and the Subscriber Identity Module (SIM). Mobile Equipment The Mobile Equipment is the hardware used by the subscriber to access the network. The mobile equipment can be Vehicle mounted, with the antenna physically mounted on the outside of the vehicle or portable mobile unit, which can be handheld. Mobiles are classified into five classes according to their power rating. CLASS POWER OUTPUT 1 20W 2 8W 3 5W 4 2W 5 0.8WCopyright © 2011 LOGTEL
  • SIM (1) The SIM is a removable card that plugs into the ME. It identifies the mobile subscriber and provides information about the service that the subscriber should receive. The SIM contains several pieces of information – International Mobile Subscribers Identity (IMSI) - This number identifies the mobile subscriber. It is only transmitted over the air during initializing. – Temporary Mobile Subscriber Identity ( TMSI ) - This number also identifies the subscriber. It can be alternatively used by the system. It is periodically changed by the system to protect the subscriber from being identified by someone attempting to monitor the radio interface. – Location Area Identity ( LAI ) - Identifies the current location of the subscriber. – Subscribers Authentication Key ( Ki ) - This is used to authenticate the SIM card. – Mobile Station International Standard Data Number ( MSISDN ) - This is the telephone number of the mobile.Copyright © 2011 LOGTEL
  • SIM (2) • Most of the data contained within the SIM is protected against reading (eg Ki ) or alterations after the SIM is issued. • Some of the parameters ( eg. LAI ) will be continuously updated to reflect the current location of the subscriber. • The SIM card can be protected by use of Personal Identity Number ( PIN ) password. • The SIM is capable of storing additional information such as accumulated call charges. FULL SIZE SIM CARD MINI SIM CARD GSMCopyright © 2011 LOGTEL
  • MSISDN Mobile Station International Subscribers Dialling Number ( MSISDN ) : Human identity used to call a MS The Mobile Subscriber ISDN (MSISDN) number is the telephone number of the MS. This is the number a calling party dials to reach the subscriber. It is used by the land network to route calls toward the MSC. CC NDC SN 98 XXX 12345 CC = Country code NDC = National Destination Code SN = Subscriber NumberCopyright © 2011 LOGTEL
  • IMSI International Mobile Subscribers Identity ( IMSI ) : Network Identity Unique to a MS The International Mobile Subscriber Identity (IMSI) is the primary identity of the subscriber within the mobile network and is permanently assigned to that subscriber. The IMSI can be maximum of 15 digits. MCC MNC MSIN 404 XX 12345..10 MCC = Mobile Country Code ( 3 Digits ) MNC = Mobile Network Code ( 2 Digits ) MSIN = Mobile Subscriber Identity NumberCopyright © 2011 LOGTEL
  • IMEI International Mobile Equipment Identity ( IMEI ) : IMEI is a serial number unique to each mobile Each MS is identified by an International Mobile station Equipment Identity (IMEI) number which is permanently stored in the Mobile Equipment. On request, the MS sends this number over the signaling channel to the MSC. The IMEI can be used to identify MSs that are reported stolen or operating incorrectly. TAC FAC SNR SP 6 2 6 1 TAC = Type Approval Code FAC = Final Assembly Code SNR = Serial Number SP = SpareCopyright © 2011 LOGTEL
  • HOME LOCATION REGISTER (HLR) • The HLR contains the master database of all subscribers in the PLMN. • This data is remotely accessed by the MSC s and VLRs in the network. The data can also be accessed by an MSC or a VLR in a different PLMN to allow inter-system and inter-country roaming. • A PLMN may contain more than one HLR, in which case each HLR contains a portion of the total subscriber database. There is only one database record per subscriber. • The subscribers data may be accessed by the IMSI or the MSISDN. • The parameters stored in HLR are – Subscribers ID (IMSI and MSISDN ) – Current subscriber VLR. – Supplementary services subscribed to. – Supplementary services information (eg. Current forwarding address ). – Authentication key and AUC functionality. – TMSI and MSRNCopyright © 2011 LOGTEL
  • VISITOR LOCATION REGISTER (VLR) • The Visited Location Register (VLR) is a local subscriber database, holding details on those subscribers who enter the area of the network that it covers. • The details are held in the VLR until the subscriber moves into the area serviced by another VLR. • The data includes most of the information stored at the HLR, as well as more precise location and status information. • The additional data stored in VLR are – Mobile status ( Busy / Free / No answer etc. ) – Location Area Identity ( LAI ) – Temporary Mobile Subscribers Identity ( TMSI ) – Mobile Station Roaming Number ( MSRN ) • The VLR provides the system elements local to the subscriber, with basic information on that subscriber, thus removing the need to access the HLR every time subscriber information is required.Copyright © 2011 LOGTEL
  • Authentication Centre (AUC) • The AUC is a processor system that perform authentication function. • It is normally co-located with the HLR. • The authentication process usually takes place each time the subscriber initializes on the system. • Each subscriber is assigned an authentication key (Ki) which is stored in the SIM and at the AUC. • A random number of 128 bits is generated by the AUC & sent to the MS. • The authentication algorithm A3 uses this random number and authentication key Ki to produce a signed response SRES( Signed Response ). • At the same time the AUC uses the random number and Authentication algorithm A3 along with the Ki key to produce a SRES. • If the SRES produced by AUC matches the one produced by MS is the same, the subscriber is permitted to use the network.Copyright © 2011 LOGTEL
  • HANDOVERCopyright © 2011 LOGTEL
  • HANDOVER • The GSM handover process uses a mobile assisted technique for accurate and fast handovers, in order to: – Maintain the user connection link quality. – Manage traffic distribution • The overall handover process is implemented in the MS,BSS & MSC. • Measurement of radio subsystem downlink performance and signal strengths received from surrounding cells, is made in the MS. • These measurements are sent to the BSS for assessment. • The BSS measures the uplink performance for the MS being served and also assesses the signal strength of interference on its idle traffic channels. • Initial assessment of the measurements in conjunction with defined thresholds and handover strategy may be performed in the BSS. Assessment requiring measurement results from other BSS or other information resident in the MSC, may be perform. in the MSC.Copyright © 2011 LOGTEL
  • HANDOVER (Cont) • The MS assists the handover decision process by performing certain measurements. • When the MS is engaged in a speech conversation, a portion of the TDMA frame is idle while the rest of the frame is used for uplink (BTS receive) and downlink (BTS transmit) timeslots. • During the idle time period of the frame, the MS changes radio channel frequency and monitors and measures the signal level of the six best neighbor cells. • Measurements which feed the handover decision algorithm are made at both ends of the radio link.Copyright © 2011 LOGTEL
  • HANDOVER MS END • At the MS end, measurements are continuously signalled, via the associated control channel, to the BSS where the decision for handover is ultimately made. • MS measurements include: –Serving cell downlink quality (bit error rate (BER) estimate). –Serving cell downlink received signal level, and six best neighbor cells downlink received signal level. • The MS also decodes the Base Station ID Code (BSIC) from the six best neighbor cells, and reports the BSICs and the measurement information to the BSS.Copyright © 2011 LOGTEL
  • HANDOVER BTS END The BTS measures the uplink link quality, received signal level, and MS to BTS site distance. The MS RF transmit output power budget is also considered in the handover decision. If the MS can be served by a neighbor cell at a lower power, the handover is recommended. From a system perspective, handover may be considered due to loading or congestion conditions. In this case, the MSC or BSC tries to balance channel usage among cells.Copyright © 2011 LOGTEL
  • HANDOVER MS IDLE TIME REPORTING During the conversation, the MS only transmits and receives for one eighth of the time, that is during one timeslot in each frame. During its idle time (the remaining seven timeslots), the MS switches to the BCCH of the surrounding cells and measures its signal strength. The signal strength measurements of the surrounding cells, and the signal strength and quality measurements of the serving cell, are reported back to the serving cell via the SACCH once in every SACCH multiframe. This information is evaluated by the BSS for use in deciding when the MS should be handed over to another traffic channel. This reporting is the basis for MS assisted handovers.Copyright © 2011 LOGTEL
  • HANDOVER MEASUREMENT IN ACTIVE MODE Downlink Frame 24 Frame 25 Idle Frame Frame 0 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 1 2 3 1 2 4 1 2 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 Frame 24 Frame 25 Idle Frame Frame 0 Uplink 1. MS receives and measures signal strength on serving cell(TS2). 2. MS transmits 3. MS measures signsl strength for at least one neighbor cell. 4. MS reads BSIC on SCH for one of the 6 strongest neighbor.Copyright © 2011 LOGTEL
  • HANDOVER NUMBER OF NEIGHBORS Maximum 32 averaging of RSS takes place. Practically a cell neighbors can be equipped for a cell. If high numbers of neighbors are equipped, then the accuracy of RSS is decreased as should have 8 to 10 neighbors. T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25Copyright © 2011 LOGTEL
  • HANDOVER NUMBER OF NEIGHBORS In one SACCH multiframe there are 104 TDMA frames. Out of this 104 frames 4 frames are idle and are used to decode the BSIC. Remaining 100 TDMA frames are used to measure RSS( Received Signal Strength) of the neighbor. If 25 neigbors are equipped, then in one SACCH multiframe each neigbor is measured 100/25 = 4 times and averaged out. This produces a less accurate value. If 10 neigbors are equipped, then in one SACCH multiframe each neigbor is measured 100/10 = 10 times and averaged out. This produces a more accurate value.Copyright © 2011 LOGTEL
  • HANDOVER INTERFERENCE ON IDLE CHANNEL GSM causes its own time interference. The MS has a omni-directional antenna. Much of the MS power goes to the server but a lot is interfering with surrounding cells using the same channel. The TDMA frames of adjacent cell are not aligned since they are not synchronised. Hence the uplink in the surrounding cell suffers from interference. Channel 10 Cell 1 Channel 10 Cell 2Copyright © 2011 LOGTEL
  • HANDOVER INTERFERENCE ON IDLE CHANNEL The BSS keeps on measuring the interference on the idle timeslots. Ambient noise is measured and recorded 104 times in one SACCH multiframe. These measurements are averaged out to produce one figure. The BSS then distributes the idle timeslots into band 0 to band 5. Since the BSS knows the interference level on idle timeslots, it uses this data to allocate the best channel first and the worst last. Inteference on idle channel measured on Idle Timeslot by BSS 0 1 2 3 4 5 6 7Copyright © 2011 LOGTEL
  • HANDOVER HANDOVER The following measurements is be continuously processed in the BSS : i) Measurements reported by MS on SACCH - Down link RXLEV - Down link RXQUAL - Down link neighbor cell RXLEV ii) Measurements performed in BSS - Uplink RXLEV - Uplink RXQUAL - MS-BS distance - Interference level in unallocated time slots Every SACCH multiframe (480 ms) a new processed value for each of the measurements is calculated..Copyright © 2011 LOGTEL
  • HANDOVER HANDOVER CONDITIONS Handover is done on five conditions – Interference – RXQUAL – RXLEV – Distance or Timing Advance – Power Budget Interference - If signal level is high and still there is RXQUAL problem, then the RXQUAL problem is because of interference. RXQUAL - It is the receive quality. It ranges from 0 to 7 , 0 being the best and 7 the worst RXLEV - It is the receive level. It varies from -47dBm to -110dBm. Timing Advance - Ranges from 0 to 63. Power budget - It is used to save the power of the MS.Copyright © 2011 LOGTEL
  • HANDOVER HANDOVER TYPES Intra-Cell Handover BSC 0 1 2 3 4 5 6 7 Call is handed BTS from timeslot 3 to timeslot 5 Handover takes place in the same cell from one timeslot to another timeslot of the same carrier or different carriers( but the same cell). Intra-cell handover is triggered only if the cause is interference. Intra-cell handover can be enabled or disabled in a cell.Copyright © 2011 LOGTEL
  • HANDOVER HANDOVER TYPES Intra-BSC Handover BSC1 0 1 2 3 4 5 6 7 BTS1 Call is handed from timeslot 3 of cell1 to timeslot 1 of cell2 . Both the cells are controlled by the same BSC. 0 1 2 3 4 5 6 7 Handover takes place between different cell which are controlled by the same BSC.Copyright © 2011 LOGTEL
  • HANDOVER HANDOVER TYPES Inter-BSC Handover BSS1 0 1 2 3 4 5 6 7 BTS1 Call is handed from timeslot MSC of cell1 to timeslot 1 of cell2 Both the cells are controlled by the different BSC. BSS2 0 1 2 3 4 5 6 7 BTS2 Handover takes place between different cell which are controlled by the different BSC.Copyright © 2011 LOGTEL
  • HANDOVER HANDOVER TYPES Inter-MSC Handover MSC1 BSS1 0 1 2 3 4 5 6 7 BTS1 Call is handed from timeslot 3 of cell1 to timeslot 1 of cell2 . Both the cells are controlled by the different BSC, each BSC being controlled by different MSC MSC2 BSS2 0 1 2 3 4 5 6 7 BTS2 Handover takes place between different cell which are controlled by the different BSC and each BSC is controlled by different MSC.Copyright © 2011 LOGTEL
  • LOCATION UPDATECopyright © 2011 LOGTEL
  • LOCATION UPDATE MSC should always know the location of the MS so that it can contact it by sending pages whenever required. The mobile keeps on informing the MSC about its current location area or whenever it changes from one LA to another. This process of informing the MSC is known as location updating. The new LAI is updated in the VLR. LAI = MCC + MNC + LAC 3 digits 1-2 digits Max 16 bits MCC MNC LAC MCC = Mobile country code. MNC = Mobile Network Code. LAC = Location area code. Identifies a location area within a GSM PLMN network. The maximum length of LAC is 16 bits. Thus 65536 different LA can be defined in one GSM PLMN.Copyright © 2011 LOGTEL
  • LOCATION UPDATE TYPES • Normal location update • Periodic location update • IMSI attach Normal Location Update 1. Mobile powers on and is idle. 2. Reads the LAI broadcast on the BCCH. 3. Compares with the last stored LAI and if it is different does a location update.Copyright © 2011 LOGTEL
  • LTECopyright © 2011 LOGTEL
  • The driving forces – The telco point of view  Addressing the trend of declining ARPU  Delivery of higher bandwidth services and capacity  Reducing OPEX & Cost/MB  Proliferation of emerging devices, with rich mobile applications and video  Quad-play (bundle)  Multiple screen offerings  Addressing shortage in bandwidth  Leveraging existing 3G infrastructure  Regulation  Re-allocation of older spectrum for 4G technologies  Open access & net neutralityCopyright © 2011 LOGTEL
  • Standards bodies IMT-Advanced 802.X – LAN/WLANCopyright © 2011 LOGTEL
  • IMT Expected Targets  IMT- Advanced (IMT-2000 – become 3G)  high quality mobile services  user equipment suitable for worldwide use  user‐friendly applications, services and equipment  worldwide roaming capability  Improve wireless performance  Better signal reception and better coverage  Increase spectrum efficiency  More subscribers and more data transfer in the same spectrum  Flat all-IP network architecture  High mobility up to 500 Km/H  enhanced peak data rates to support advanced services and applications  100 Mbit/s (UL 50 Mbit/s DL) for high mobility  1 Gbit/s for low mobility  Low latency <50msCopyright © 2011 LOGTEL
  • 4G Enabling Technology  Some key technologies made 4G possible  Both WiMAX and LTE use:  OFDM, OFDMA and SC-FDMA  Channel dependent scheduling  Adaptive coding and modulation (ACM)  Multiple-In-Multiple-Out (MIMO) antenna processing  Turbo coding and decodingCopyright © 2011 LOGTEL
  • OFDMA Flexibility  With OFDMA the user allocation is flexible  Can change from frame to frame  Multiple allocations for several applications  Allocation changes  In WiMAX every 5 ms  In LTE every 1 ms Burst Burst time Burst OFDMA frequency frequencyCopyright © 2011 LOGTEL
  • Single Carrier FDMA (SC-FDMA)  A major problem with OFDM and OFDMA is high peak-to-average power ratio (PAPR)  Transmitted amplitude with large variation  Requires a linear amplifier at transmitter  Linear amplifies consumes high power  OK at base station  For mobile station, this consumes battery  LTE uses a solution for UL: SC-FDMA  Single carrier transmissionCopyright © 2011 LOGTEL
  • MIMO  Transmit diversity:  Same modulation symbols sent from all Tx M antennas  Receiver combines the signal from N antennas  Useful to increase performance against fading  Spatial multiplexing:  Different modulation symbols sent from M Tx antennas  Receiver received the signal from N antennas  Useful to increase data rate if channel is good  WiMAX uses up to 2x2. LTE uses up to 4x4Copyright © 2011 LOGTEL
  • MIMO Radio Channel  Multiple antennas at both the base station and terminal can significantly increase data rates with sufficient multipath  Reduce noise  Reduce handoffs and disconnectingCopyright © 2011 LOGTEL
  • So, What will be the bandwidth ?Copyright © 2011 LOGTEL
  • WiMax is dead (?)Copyright © 2011 LOGTEL
  • LOCATION UPDATE MS BSS MSC RACH Imme. Assign Location update request Authentication request Authentication response DTI<CICMD> Cipher mode command Cipher mode complete DTI<CICMP> Location update acceptedCopyright © 2011 LOGTEL
  • IMSI ATTACH Saves the network from paging a MS which is not active in the system. When MS is turned off or SIM is removed the MS sends a detach signal to the Network. It is marked as detached. When the MS is powered again it reads the current LAI and if it is same does a location update type IMSI attach. Attach/detach flag is broadcast on the BCCH sys info. PERIODIC LOCATION UPDATE Many times the MS enters non-coverage zone. The MS will keep on paging the MS thus wasting precious resources. To avoid this the MS has to inform the MSC about its current LAI in a set period of time. This time ranges from 0 to 255 decihours. Periodic location timer value is broadcast on BCCH sys info messages.Copyright © 2011 LOGTEL
  • DISCONTINOUS TRANSMISSION During conversation user talks alternatively. In DTX mode of operation the transmitter are switched on only for frames containing useful information. Helps to increase battery life and reduce interference level. T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SID T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 T T T T T T T T T T T T S T T T T T T T T T T T T I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25Copyright © 2011 LOGTEL
  • IMPLEMENTATION OF DTX Voice Activity Detector ( VAD ) 20 ms speech VAD Speech / No speech block Determines which specific block of 20ms from the speech coder contains speech. Removes stationary noise. Inserts comfort noise. The frames containing this background noise are called SID frames and are sent in blocks of 8 frames within every 104 frame block.Copyright © 2011 LOGTEL
  • Thank You!!! 1 4Copyright © 2011 LOGTEL