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Mobile systems evolution(f)


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  • Özünüz haqqında qısa məlumat
  • agenda
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    • 1. GSM system evolution By Rahim Ahmedov
    • 2. About Me• Born at 1981, Sumgait • Works at Azercell, as• Graduate from senior engineer, Azerbaijan State ICT/Service Network Economic University Operations/ Billing & charging/ data processing and roaming team • Rahim.ahmedov@gmail .com
    • 3. Key Topics• Introduction• GSM system overview• 3G overview• LTE (4G) overview
    • 4. Evolution path 4G - 1GBit LTE 299 MBit 3G 14.4 MBit • Launched at 14 December 2009 • In 2005, the by TeliaSonera in first HSDPA (High- Oslo and 2.5G 384 KBit Speed Downlink Stockholm • In 2000, GPRS Packet Access) • Download speed launched capable network at 299.6 MB, • In 2001 the first became upload 75.4 MB 2G 14.4 KBit operational. UMTS (W-CDMA) • 49 Commercial • 1st GSM call at network was • The LTE Networks July 1, 1991 launched first HSUPA (High- • 1st SMS sent at • In 2002 MMS Speed Uplink 1992 introduced Packet Access)1G network was • 1st Roaming at • In launched in 2007• 1st was launched in 1992 2003 EDGE services with up-link Japan by NTT in 1979 first became speeds up to operational• Based on analog 5.76 MBit telecom standard
    • 6. GSM system components
    • 7. GSM Geographical Network Structure• Cell – Is a basic unit of cellular system & Is defined as the area of radio coverage• Location area (LA) – Is defined as a group of cells – Within network subscriber location is linked to LA – When an MS crosses the boundary between 2 cell belonging to different LAs, new LA is reported to network – When there is call to MS, a paging message is broadcast within all the cells belonging to the network• MSC Service Area – Is made up of number of LA’s, – Represents the geographical part of the network controlled by one MSC• PLMN Service Area – Public land mobile network is a one operators service area• GSM Service area – Is the entire geographical area in which subscriber can gain access to GSM network
    • 8. GSM Core- Switching Subsystem• Basic elements are – MSC/VLR: Mobile Switching center/visitor location register – GMSC: Gateway MSC – HLR: Home location register – AUC: Authentication center – SGSN: Serving GPRS support node – GGSN: Gateway GPRS support node
    • 9. GSM Core - Switching Subsystem: MSC• Switching & call routing – Controls call setup, supervision an release – Interacts with other network nodes• Charging – During a call it records call related information and stores it in a file. – The file then is used for postpaid charging (offline)• Service provisioning – Supplementary services are provided & managed in MSC – SMS service is handled in MSC• Communication with HLR – During call setup to MS, HLR request some routing information from MSC• Communication with VLR – During call setup and release MSC requests subscription information from VLR• Communication with other MSC – Communicates during handovers between cells belonging to different MSCs• Control of connected BSC (Base station controllers) – Each MSC can control several BSCs – Communicate with BSCs during call setup & handovers between 2 BSCs
    • 10. GSM Core - Switching Subsystem: VLR• VLR acts as a temporary storage of subscription information of MSs, which are within particular MSC service area• Each MSC has one VLR, usually MSC & VLR are implemented as a one hardware• When MS moves to new MSC service area: – VLR queries its database for the MS – When VLR finds no records, it sends request to HLR – HLR passes information to VLR and updates location information of subscriber – HLR instructs old VLR to delete information about this MS – VLR stores subscription information of new MS, including latest location & status.• VLR stores following information: – MS identity numbers – MS supplementary services ( for ex. call forwarding on busy) – MS status (for ex. Idle) – MS current LA
    • 11. GSM Core - Switching Subsystem: GwMSC• Main function is to interrogate HLR in order to route a mobile terminating call• GMSC request call routing information from the HLR, that provides information about which MSC/VLR to route the call• Gateway functions are: – Find and interrogate HLR for roaming number – Route the call according to interrogation
    • 12. GSM Core - Switching Subsystem: HLR• HLR is a centralized DB that stores and manages all MSs of operators• HLR stores – MS identity (MSISDN, IMSI) – MS supplementary services – MS location information – MS authentication information• Main functions of HLR – Subscription database management – Communications with MSC • When setting up calls to a MS, HLR contacts MSC serving the MS for routing information – Communication with GMSC • When setting up calls to a MS, GMSC requests MS location information from HLR, then HLR provides this in the form of routing information – Communication with AUC – Communication with VLR
    • 13. GSM Core - Switching Subsystem: AUC• AUC main function is to provide information - triplet, which is used by MSC to perform – Subscriber authentication – Radio information ciphering• Triplet consist of – Non predictable random number (RAND) – Signed response (SRES) – Ciphering Key (Kc)
    • 14. GPRS Support nodes• Serving GPRS support node (SGSN) – Forwards incoming & outgoing IP packets addressed to/from MS that is attached within the SGSN service area – It provides packet routing & transfer to and from the SGSN service area – SGSN also provides • Ciphering & authentication • Session management • Mobility management • Logical link management towards the MS • Connection to HLR, MSC, BSC, SMS-GMSC, SMS-IWMSC, GGSN • Output of charging data• Gateway GPRS support node (GGSN) – Provides the interface towards the external IP packet networks – Contains access functionality that interfaces ISP functions like routers & RADIUS servers – Acts as a router for IP addresses of all subscribers served by the GPRS network
    • 15. GPRS Support nodes (2)
    • 16. RADIO ACCESS NETWORK ELEMENTS• Main functions are – Radio communication with MS – Handover of calls – Management of radio network resources and cell configuration data• RAN main components – BSC: Base station controller – TRC: Transcoder controller – RBS: Radio base station
    • 17. RADIO ACCESS NETWORK ELEMENTS: BASE STATION CONTROLLER (BSC)• Main functions are: – Radio network management – RBS management – Multi Band support – TRC handling – Transmission network management – Internal BSC operation and maintenance – Positioning services – Handling of MS connections – GSM-UMTS Cell reselection and handover
    • 18. RADIO ACCESS NETWORK ELEMENTS: BSC MAIN FUNCTIONS• Radio network management – Administration of radio network data • Traffic management: management of TCH(Traffic CHannel), management of PDCH (Package Date Channel) • Cell description data: cell identity, BCCH (Broadcast Control CHannel) channel number, RBS type, maximum – minimum output powers in the cell • System information data: information about cell statuses, maximum output powers in the cell, BCCH identities in neighboring cells • Location data • Cell load sharing data: parameters for forcing early handovers from congested cells, GSM/WCDMA handovers – Traffic and event measurements • Number of call attempt, Number of congestions, Traffic levels for a cell, Traffic levels for a MS, Number of handovers, Number of dropped connections – Idle channel measurement • Based on collected statistics allocates channel with low interference
    • 19. RADIO ACCESS NETWORK ELEMENTS: BSC MAIN FUNCTIONS (2)• RBS Management• Multi Band Support – Capable for handling RBS equipment from more than one frequency• Transmission network management – Transmission interface handling – High speed signaling link• GSM-UMTS cell reselection & handover – Capable for roaming between GSM cells without loss of the service
    • 20. RADIO ACCESS NETWORK ELEMENTS: BSC MAIN FUNCTIONS (3)• Handling of MS connections – During call setup • Paging: sends paging messages to RBSs defined within the desired LA • Signaling setup: MS connection is transferred to SDCCH (Standalone Dedicated Control Channel). If MS initiated the connection, the BSC checks its processor load • Assignment of TCH: after SDCCH assignment, the call setup continues with the assignment of TCH – During a call • Dynamic power control in MS and RBS: calculates adequate MS & RBS output power based on the received measurements of the uplink & downlink each 480 ms. • Locating: continuously evaluates the radio connection to MS and if necessary suggests a handover • Handover: decides which cell to handover to and begins the handover process • Frequency hopping: – Baseband hopping: hopping between frequencies on different transceivers in a cell – Synthesizer hopping: hopping between frequencies on same transceivers in a cell
    • 21. RADIO ACCESS NETWORK ELEMENTS: RADIO BASE STATION MAIN FUNCTIONS• Radio resources handling – Configuration & system start – Radio transmission up to 35 km for normal GSM limit – Radio reception• Extended range – Radio transmission up to 121 km• Signal processing – Ciphering – Channel coding & interleaving – Adaptive equalization – Realization of diversity – Demodulation• Signal link management• Synchronization – Synchronize with the correct frequency reference & TDMA frame number
    • 22. Radio access method for 2G• GSM uses TDMA (Time division multiple access) as the main radio access method• TDMA allows several users to share the same frequency channel by dividing the signal into different time slots.• The users transmit in rapid succession, one after the other, each using its own time slot.
    • 23. TDMA Frame• In GSM, A frequency is divided up into 8 time slots• Each time slot lasts 576.9 µs. A time slot is the basic radio resource used to facilitate communication between the MS and the BTS• GSM uses Gaussian Minimum-Shift Keying (GMSK) as its modulation method. GMSK provides a modulation rate of 270.833 kilobits per second (kb/s). At that rate, a maximum of 156.25 bits can be transmitted in each time slot (576.9 µs). – 156.25b = 270.833Kb *1000/1000000 * 576.9 µs• The data transmitted during a single time slot is known as a burst.
    • 24. TDMA Normal Burst• Tail Bits - Each burst leaves 3 bits on each end in which no data is transmitted. This is designed to compensate for the time it takes for the power to rise up to its peak during a transmission. The bits at the end compensate for the powering down at the end of the transmission.• Stealing Flags - Indicates whether the burst is being used for voice/data (set to "0") or used for singalling (set to "1")• Training Sequence - The training sequence bits are used to overcome multi-path fading and propagation effects through a method called equalization.
    • 25. TDMA Frame Structure & Hierarchy• A Multiframe is composed of multiple TDMA frames.• There are two types of multiframes: – Control Channel Multiframe • composed of 51 TDMA frames; duration = 235.4 ms – Traffic Channel Multiframe • composed of 26 TDMA frames; duration = 120 ms• In the example, the MS has been allocated a Traffic Channel in TS2. Therefore the MS will only transmit/receive during TS2 of each TDMA frame.
    • 26. 3G OVERVIEW
    • 27. 3G core network
    • 28. MSC Server functions• Connection management• Mobility management – Roaming (within WCDMA, between WCDMA and GSM) – Handover (inter MSC, intra MSC from WCDMA to GSM) – Security (Subscriber authentication, ciphering) – Charging• Supported services – Teleservices – voice, SMS – Bearer services – CS based data up to 64 Kb/s – Supplementary services – call forward, call waiting, call holding, call conference – USSD (unstructured supplementary service data) – IN and CAMEL (customized applications for mobile enhanced logic) services – prepaid charging, VPN
    • 29. Media Gateway for mobile network• M-MGw handles payload processing, traffic and signaling interworking between networks• M-MGw functions – Speech coding – Interactive messaging – Tone sending – DTMF – Conferencing – Data volume counting
    • 30. Radio access interface for 3G• Common air interface for 3G is WCDMA (Wideband Code Division Multiple Access) 1• CDMA is a spread-spectrum 0.8 technology that employs codes to separate users in the same 0.6 frequency spectrum 0.4• Unlike TDMA, in CDMA all 0.2 Code 3 users share same frequency at 0 Code 1 the same time within cell 5 MHz• CDMA is a form of Direct Sequence Spread Spectrum communications
    • 31. CDMA direct sequence spread spectrum
    • 32. Spreading principles• A bit of information 0, 1 (binary) or 1,-1 (bipolar)• Bits are spread into a number of chips when it is multiplied with spreading code• Chip rate for a system is constant 3.84 Mchip/s• The spreading factor (SF) is the ratio between the chip rate and symbol rate (bit rate)• The same code is used for de-spreading the information
    • 33. Bits and chips 1 0 1 +1Bipolardata Bits/ssequence -1 +1Code Chips/s(1 -1 1 -1) -1 +1Signal Chips/s -1
    • 34. Spreading code groupsWCDMA uses 2 group of codes:• Channelization codes: used for channel separation of transmission from one transmitter (UE/BS)• Scrambling codes (pseudo noise codes): used to distinguish between different transmitters (UE/BS)
    • 35. Modulation• Quadrature Phase Shift Keying (QPSK) is used in WCDMA for modulation
    • 36. LTE OVERVIEW
    • 37. 3G challenges LTE solutions3G challenges LTE solutionsData rates are too low for high Advanced radio technologiesbandwidth services (like video) (OFDM, multiple antenna techniquesDelays and latencies are too All-IP code networks forhigh for real time services (like seamless mobility and VoIPvoice3G networks are not optimized Advanced services and mobilefor IP based multimedia broadband servicesservices
    • 38. Wish list for LTE >100 Mbps downlink >50 Mbps uplink <10 ms latency for radio network <50 ms latency for end to end Better spectral efficiency lower cost interworking with 3G
    • 39. LTE Architecture• Entire system composed of both LTE is called the Evolved Packet System (EPS)• At a high-level, the network is comprised of: – Core Network (CN), called Evolved Packet Core (EPC) – access network (E-UTRAN – Evolved Universal Terrestrial Radio Access Network)• A bearer is an IP packet flow with a defined QoS between the gateway and the User Terminal (UE)• CN is responsible for overall control of UE and establishment of the bearers
    • 40. LTE Network schema
    • 41. E-UTRAN• Unlike 3G E-UTRAN is decentralized, there is no RNC• E-UTRAN is pure IP based• Contains only eNBs (evolved Node B)• eNBs are interconnected by X2 interface to coordinate handovers and data transfer
    • 42. E-UTRAN: evolved Node B• Radio resource management• IP header compression and encryption• Uplink/downlink radio resource allocation• Transfer of paging massages• Transfer of broadcast information• Selection of MME (mobility management entity) when UE attaches to the network• Handover management
    • 43. E-UTRAN: X2 interface• Control pane – Intra LTE access system mobility support – Context transfer from one eNB to other – Tunneling of user packages – Handover cancellation – Uplink load management – X2 uses SCTP (Stream Control Transmission Protocol) as the transport layer protocol• User pane – Tunneling end user packets between eNBs – Identifies packets with tunnels and packet-loss management – Uses GTP-U over UDP/IP
    • 44. S1 interface• S1 is interface between E-UTRAN and EPC• S1 control pane functionalities – Delivering signaling between eNB and MME – Uses SCTP over IP – Application signaling protocol is S1-AP – EPS bearer setup and release – Handover signaling procedure – Paging procedure – NAS transport procedure• S1 user pane functionalities – Delivering user data between eNB and S-GW – Consists of GTP-U over UDP/IP – One GTP tunnel per radio bearer carries user traffic – IP differentiated Service Code Point (DSCP) marking is supported for QoS per radio bearer
    • 45. EPC: Mobility Management Entity (MME)• Managing and storing UE contexts• Generating temporary identifiers for Ues• Idle-state mobility control• Distributing paging message to eNBs• Security control• Roaming• Authentication• Bearer control
    • 46. EPC: Serving Gateway (S-GW)• There are 2 types of gateway in EPC, one facing E- UTRAN and one facing external packet data network• A UE can connect only one S-GW, but multiple P- GW• S-GW functions – Anchoring the user plane for inter –eNB handover – Anchoring the user plane for inter –3GPP mobility – Similar to SGSN in 3G network – Packet routing and forwarding
    • 47. EPC: Packet Data Network Gateway• P-GW is similar to GGSN in 3G• Provides connectivity to the PDN• Allocates IP addresses to UE• Accounting and QoS• Anchoring user place for mobility during inter MME/S-GW handovers, LTE and 3G handovers, 3G and non 3GPP network handovers
    • 48. EPC: Home Subscriber Server (HSS)• HSS is a user database that stores subscription related information• HSS is storehouse for user identification, numbering and service profiles• Replace HLR in LTE
    • 49. LTE Air interface• OFDMA (orthogonal frequency division multiple access) is used as radio access interface• OFDM advantages – Scalable design: allows the radio technology to utilize a variable bandwidth using same radio access technology (up to 20 MHz) – Time and frequency scheduling: – Reduced interference – Higher data rates – Support for smart antennas: multiple antenna techniques
    • 50. The OFDM advantage• Signals are said to be orthogonal when they do not interfere with each other: – For ex: signal is orthogonal in time domain if they occur on the same frequency but not at the same time• OFDM allows guard bands to be omitted by – Separating subcarriers by the inverse of modulation rate – Ensure that modulation rate is the same on all subcarriers – Ensure that there is only integer number of radio carrier cycles during modulation symbol time Saved bandwidth
    • 51. Simplified view of OFDMA 10 Mbps OFDMA 100 kbps100 kbps 100 kbps 100 kbps …
    • 52. Multiple antenna benefits• Better overall signal quality• Improved spectral efficiency• Higher capacity• Reduced power consumption• Lower interference• Improved coverage
    • 53. Multiple antenna techniquesMultiple antenna techniques MIMO/spatial Diversity Beam forming multiplexing Space Single Multi SimpleReceive Transit division user user beamdiversity diversity multiple MIMO MIMO forming access
    • 54. Diversity
    • 55. Single user MIMO
    • 56. Multi user MIMO