Modern wireless communications_ASRao


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Modern wireless communications_ASRao

  1. 1. Wireless Communications Modern A.Sanyasi Rao AMIE; M.Tech; MISTE; MIETE Assoc. Professor Balaji Inst. of Engg. & Sci., Narsampet
  2. 2. ASRao “Things that think… don’t make sense unless they link.”
  3. 3. ASRao Commonly used Devices Tablet PC Handheld device Cell Phone Kindle- e book reader Watch mobile Phone
  4. 4. ASRao Wireless Characteristics – Communication without wires – Wires are replaced by electromagnetic waves – electromagnetic waves carry a signal through atmospheric space – use radio frequency RF waves, which ranges from 3 kHz to 300 GHz – or infrared IR, which ranges from 3 THz to 430 THz
  5. 5. Electromagnetic Spectrum Showing Radio Frequency ASRao
  6. 6. ASRao What is Mobility? Two types of mobility: i)Device portability ii)User Mobility no mobility mobile wireless user, using same access point high mobility mobile user, connecting/ disconnecting from network Mobility Spectrum mobile user, passing through multiple access point while maintaining ongoing connections
  7. 7. Degrees of Mobility ASRao • Walking Users • Low speed • Small roaming area • Usually uses high-bandwidth • Vehicles • • • • High speeds Large roaming area Usually uses low-bandwidth Uses sophisticated terminal equipment (cell phones)
  8. 8. ASRao ORIGIN of Wireless Communication 1864 James 1886 Maxwell Rudolph Predicts existence of radio waves. Hertz Demonstrates radio waves. J C Bose In 1895 Bose gave his first public demonstration of electromagnetic waves, using them to ring a bell remotely (more than a mile) and to explode some gunpowder 1895-1901 Guglielmo Marconi Demonstrates wireless communications over increasing distances at 13 May 1897
  9. 9. ASRao 1980s Analog Voice 1G AMPS Typical 2.4 Kbps NMT TACS
  10. 10. ASRao First Generation • Early Wireless communications – Signal fires – Morse Code – Radio Radio Transmitter 1928 Dorchester
  11. 11. ASRao 1G • Advanced Mobile Phone Services (AMPS) – Deployed in US , Japan : 1983 • Nordic Mobile Telephony (NMT) – Sweden, Denmark, Norway, Finland : 1981 • Total Access Communication System (TACS) – British System, similar to AMPS : 1985
  12. 12. ASRao 1990s Digital Voice 2G GSM 9.6 - 14.4 Kbps (circuit data) TDMA CDMA
  13. 13. ASRao Circuit Switching Dedicated end to end connection A private road all for yourself
  14. 14. ASRao Packet Switching Divided packets can take different paths and times A shared highway
  15. 15. ASRao The Second Mobile Generation 2G • The second generation (2G) of the wireless mobile network was based on low-band digital data signaling. • The most popular 2G wireless technology is known as Global Systems for Mobile Communications (GSM). • The first GSM systems used a 25MHz frequency spectrum in the 900MHz band.
  16. 16. ASRao 2G Technologies • Global System Mobile (GSM) • Interim-Standard 136 (IS-136) or North America Digital Cellular (NADC) or US Digital Cellular (USDC) • Pacific Digital Cellular (PDC) • Interim-Standard 95 Code Division Multiple Access (CDMA) (IS-95 or cdmaOne)
  17. 17. ASRao 2G – GSM • Global system for Mobile – Based on TDMA ; Europe – 900 Mhz, 1800 Mhz. – Later 850 Mhz and 1900 Mhz in America – World Phones
  18. 18. ASRao GSM Architecture • The available 25MHz of bandwidth into 124 carrier frequencies of 200 kHz each. • Each frequency is then divided using a TDMA scheme into 8 timeslots and allows eight simultaneous calls on the same frequency. • TDMA breaks down data transmission, such as a phone conversation, into fragments and transmits each fragment in a short burst, assigning each fragment a time slot. • Today, GSM systems operate in the 900MHz and 1.8 GHz bands throughout the world with the exception of the Americas where they operate in the 1.9 GHz band.
  19. 19. GSM Architecture ASRao •Home location register (HLR) database – stores information about each subscriber that belongs to it. •Visitor location register (VLR) database – maintains information about subscribers physically in the region currently •Authentication center database (AuC) – used for authentication activities and holds encryption keys •Equipment identity register database (EIR) – keeps track of the type of equipment that exists at the mobile station
  20. 20. ASRao Interim Standard-136 (IS-136) • Started in 1991 • Also known as North American Digital Cellular (NADC) or US Digital Cellular (USDC) • Uses p/4-DQPSK, speech coding • Uses TDMA with 3 time slotted users for each 30 kHz radio channel. • Capacity improvement is 3 times that of AMPS and later 6 times due to advancement in DSP
  21. 21. ASRao Interim Standard-95 (IS-95) [cdma One (or) 2G-CDMA] • It is a popular 2G CDMA standard. • The main advantage of CDMA is that many more users (up to 10 times more) can be supported as compared to TDMA. • Convolutional Channel coding used • Modulation technique used is BPSK • Supports up to 64 users that are orthogonally coded and simultaneously transmitted on each 1228 KHz channel. • Major success in Korea, Used by Verizon and Sprint • Easy Migration to 3G
  22. 22. ASRao The IS-95 cellular system has different structures for its forward (base station to mobile station) and backward links. Forward Channel Reverse Channel The forward link consists of up to 64 logical CDMA channels, each occupying the same 1228 kHz bandwidth. The forward channel supports different types of channels: •Traffic channels (channels 8 to 31 and 33 to 63) – these 55 channels are used to carry the user traffic (originally at 9.6 Kbps, revised at 14.4 Kbps). •Pilot (Channel 0) – used for signal strength comparison, among other things, to determine handoffs •Synchronization (Channel 32) – a 1200 bps channel used to identify the cellular system (system time, protocol revision, etc.). •Paging (channels 1 to 7) – messages for mobile stations
  23. 23. ASRao • All these channels use the same frequency band – the chipping code (a 64-bit code) is used to distinguish between users. • Thus 64 users can theoretically use the same band by using different codes. This is in contrast to TDMA where the band has to be divided into slots – one slot per user. • The voice and data traffic is encoded, assigned a chipping code, modulated and sent to its destination. • The data in the reverse travels on the IS-95 reverse links. The reverse links consist of up to 94 logical CDMA channels, each occupying the 1228 kHz bandwidth. • The reverse link supports up to 32 access channels and up to 62 traffic channels. • The reverse links support many mobile unit-specific features to initiate calls, and to update location during handoffs.
  24. 24. ASRao 2G CDMA (IS-95) Network Architecture •The overall architecture of 2G CDMA-based systems are similar to the TDMAbased GSM systems. •The main difference is that the radio communication between the Base Station Subsystem and Mobile System uses CDMA instead of TDMA.
  25. 25. ASRao 2001 2.5G GPRS Packet Data
  26. 26. ASRao Why 2.5G ? • The Second Generation (2G) wireless networks are mostly based on circuit-switched technology which limit the data user to a single circuit switched voice channel • 2G are thus, limited to data throughput rate of an individual user (approx on the order of 10kbps) • In 2G, original GSM, CDMA, and IS-136 standards which originally supported 9.6 kilobits per second transmission rates for data messages. • 2G wireless technologies can handle some data capabilities such as fax and short message service (SMS) at the data rate of up to 9.6 kbps, but it is not suitable for web browsing, rapid email, and multimedia applications.
  27. 27. ASRao 2.5G Standards • So-called „2.5G‟ systems are introduced to enhance the data capacity of GSM and mitigate some of its limitations. • These systems add packet data capability to GSM networks. • 2.5G standards are IS-95B, HSCSD, GPRS, EDGE technologies. • IS-95B (CDMAOne is upgraded which uses higher data rate than IS-95 and more efficient Handoff techniques)
  28. 28. ASRao Features of 2.5G • It allow existing 2G equipment to be modified and supplemented with new infrastructure to support high data rate transmission for – – – – – Web browsing Email Mobile-Commerce (m-commerce) Location based mobile services Support Wireless Application Protocol (WAP) • WAP is web browsing format language that allows standard web pages to be viewed in a compressed format
  29. 29. ASRao 2.5G - GPRS • General Packet Radio Service - An Overlay technology on top of the existing GSM systems. • GPRS (General Packet Radio Services) is a packet based data network. – Unlike HSCSD, which dedicates circuit switched channels to specific users, GPRS supports circuit switching for multi-user network sharing of individual radio channels and time slots. • GPRS can theoretically provide IP-based packet data speeds up to a maximum of 160 Kbps. • Typical GPRS networks operate at lower data rates. One proposed configuration is 80 Kbps maximum (56 Kbps typical) for the downlink and 20 Kbps maximum (14.4 Kbps typical) for the uplink.
  30. 30. ASRao •GPRS can be added to GSM infrastructures quite readily. •It takes advantage of existing 200 kHz radio channels and does not require new radio spectrum. •GPRS basically overlays a packet switching network on the existing circuit switched GSM network. This gives the user an option to use a packet-based data service. •The main component of a GPRS network is the GSN (GPRS Support Node) that receives the packet data and transfers it to the Internet or other GPRS networks. •To provide GPRS services on top of GSM, the network operators need to add a few GSNs and make a software upgrade to BSCs and few other network elements. This quick upgrade capability has fueled the popularity of GPRS. • Efficient – as resources not tied up all the time.
  31. 31. ASRao GPRS Network Architecture
  32. 32. ASRao Comparison of GSM & GPRS Data Rates Modulation Technique Billing Type of Connection GSM 9.6 Kbps GPRS 14.4 to 115.2 Kbps GMSK GMSK Duration of connection Circuit – Switched Technology Amount of data transferred Packet - Switched Technology
  33. 33. ASRao HSCSD • High-Speed Circuit-Switched Data. • An enhancement to CSD – Multiple timeslots used. • Data rates up to 38.4 Kbps (4 times CSD). – In reality supports 14.4Kbps. • Expensive than CSD. • HSCSD (High Speed Circuit Switched Data) use a circuit switched technique in GSM network. Uses consecutive time slots instead of one which increases the data rate from 9,600 bps to 14,400 bps. By using 4 consecutive time slots it increases to 57.6 kbps. • Inefficient – as resources ties up all the time, even when nothing sent.
  34. 34. ASRao • HSCSD is ideal for dedicated streaming Internet access or real-time interactive web sessions • HSCSD is a specification for data transfer over GSM networks. HSCSD utilizes up to four 9.6Kb or 14.4Kb time slots, for a total bandwidth of 38.4Kb or 57.6Kb. • 14.4Kb time slots are only available on GSM networks that operate at 1,800Mhz. • 900Mhz GSM networks are limited to 9.6Kb time slots. • Therefore, HSCSD is limited to 38.4Kbps on 900Mhz GSM networks. • HSCSD can only achieve 57.6Kbps on 1,800Mhz GSM networks.
  35. 35. HSCSD vs. GPRS ASRao • HSCSD has an advantage over GPRS in that HSCSD supports guaranteed quality of service because of the dedicated circuit-switched communications channel. This makes HSCSD a better protocol for timing-sensitive applications such as image or video transfer. • GPRS has the advantage over HSCSD for most data transfer because HSCSD, which is circuit-switched, is less bandwidth efficient with expensive wireless links than GPRS, which is packet-switched. • For an application such as downloading, HSCSD may be preferred, since circuit-switched data is usually given priority over packet-switched data on a mobile network, and there are few seconds when no data is being transferred.
  36. 36. ASRao 2003 Packet Data 2.75G EDGE CDMA 1xRTT
  37. 37. ASRao EDGE • EDGE (Enhanced Data rate for GSM) • Superset of GPRS. • Data rate = 4 times GPRS. • EDGE (Enhanced Data rate for GSM Evolution) introduces 8-PSK in addition to GSM‟s standard GMSK modulation. – EDGE allows for 9 different air interface formats known as multiple modulation and coding schems (MCS) with varying degree of error control protection.
  38. 38. ASRao EDGE (Enhanced Data Rates for Global Evolution) – – – – – – – – – – EDGE is add-on to GPRS Uses 8-PSK modulation in good conditions Increase throughput by 3x (8-PSK – 3 bits/symbol vs GMSK 1 bit/symbol) Offer data rates of 384kbps, theoretically up to 473.6kbps Uses 9 Modulation coding schemes (MCS1-9) MCS(1-4) uses GMSK, while MCS(5-9) uses 8PSK modulation. Modulation Bit rate – 810kbps Radio data rate per time slot – 69.2kbps User data rate per time slot – 59.2kbps (MCS9) User data rate (8 time slots) – 473.6kbps • New handsets / terminal equipment; additional hardware in the BTS, Core network and the rest remains the same • EDGE access develops to connect to 3G core
  39. 39. ASRao Coding Schemes for EGPRS
  40. 40. ASRao Evolved EDGE • Data rate = 1Mbps • Encoding technique – 32QAM and 16QAM. • Requires simple network enhancements with software update.
  41. 41. IS-95B ASRao IS-95B is the evolved version of IS-95A and is designated as 2.5G. IS-95B is capable of providing for higher speed data services. The following are the key aspects of the standard: • Theoretical data rates of upto 115 kbps, with generally experienced rates of 64 kbps • Additional Walsh codes and PN sequence masks, which enable a mobile user to be assigned up to eight forward or reverse code channels simultaneously, thus enabling a higher data rate • Code channels, which are transmitted at full data rates during a data burst • Convolution Channel coding • Binary Phase Shift Keying (BPSK) as the Modulation technique used
  42. 42. CDMA 1xRTT ASRao • 1x is an abbreviation of 1xRTT (1x Radio Transmission Technology).1x refers to the no. of duplex radio channels. • Supports 33-35 simultaneous voice calls per 1.25MHz. • Encoding technique: – BPSK for forward and reverse link. • Supports theoretical data rates of upto 307 kbps, with generally experienced rates of 144 kbps • Quality and Erasure indicator bits (QIB and EIB) on the reverse power control sub channel. These help in indicating to the BS about bad frames or lost frames received at the mobile station, so that they can be retransmitted. • Convolutional and Turbo coding techniques used • Modulation technique used is QPSK • Software and minimum hardware update.
  43. 43. ASRao Migration from 2G to 3G 2G 2.5G IS-95 GSM- GPRS IS-95B HSCSD Cdma2000-1xRTT 3G IS-136 & PDC EDGE W-CDMA EDGE Cdma2000-1xEV,DV,DO Cdma2000-3xRTT 3GPP2 TD-SCDMA 3GPP
  44. 44. ASRao GSM Evolution to 3G HSCSD GSM GPRS EDGE WCDMA
  45. 45. ASRao 114 Kbps GPRS 384 Kbps EDGE 3GPP 100 Mbps LTE 3GPP (3G Partnership Project for Wideband CDMA standards based on backward compatibility with GSM and IS-136/PDC 1.92 Mbps WCDMA 14 Mbps HSPA
  46. 46. ASRao 114 Kbps 1xRTT 3GPP2 3GPP2 (3G Partnership Project for cdma2000 standards based on backward compatibility with IS-95). 2.4 Mbps EV-DO 288 Mbps UMB (abandoned 2008 Nov & favoring LTE)
  47. 47. ASRao CDMA2000 IMT2000 3G W-CDMA (UMTS)
  48. 48. 3G Wireless Networks ASRao • 3G uses a technique called CDMA, in which multiple users use the same frequency and time. • For more efficient use of resources, one wishes to allow more users to transmit simultaneously. •It has very high data transfer rate. •Works equally well with both mobile and PC. •Works at higher frequency than 1G and 2G. •Multimedia services add high speed data transfer to mobile devices, allowing new video, audio and other applications (including Internet Services) through mobile phones. • Improved voice quality. • symmetrical and asymmetrical data transmission. • Global roaming across networks. • Improved security.
  49. 49. ASRao Applications of 3G • Mobile Television • Video Calling • wireless Internet • Audio/Video On Demand • e-Post Cards • Secure Mobile Communications • Video Conferencing • Traffic & Travelling Information
  50. 50. ASRao 3 G W-CDMA (UMTS) • UMTS - Universal Mobile Telecommunications System. Also known as W-CDMA. • W-CDMA uses the DS-CDMA and TDD channel access method with a pair of 5 MHz channels. • Requires new cell towers & frequency allocations. • Frequency bands: – Uplink 1885-2025 MHz (mobile-to-base ) – Downlink 2110-2200 MHz (base-to-mobile).
  51. 51. ASRao • UMTS, or W-CDMA, assures backward compatibility with the 2G GSM, IS136, and PDC TDMA technologies, as well as all 2.5G TDMA technologies Although W-CDMA is designed to provide backward compatibility and interoperability for all GSM, IS-136/PDC, GPRS, and EDGE switching equipment and applications, it is clear that the wider air interface bandwidth of W-CDMA requires a complete change out of the RF equipment at each base station. •W-CDMA is for both wide area mobile cellular coverage (using FDD) as well as indoor cordless type applications (using TDD). • Designed for “Always-ON” packet-based wireless service so that computers, mobiles and laptops etc. may all share the same wireless network to be connected to the Internet anytime, anywhere. • W-CDMA supports data rates upto 2.408 Mbps per user to allow high quality data, multimedia and streaming video broadcasting services. • Requires a minimum spectrum allocation of 5 MHz where a channel (5 MHz) will be able to support 100 to 350 simultaneous voice calls at once.
  52. 52. ASRao • UMTS, in the terrestrial component has 3 types of cells: - macro cell - micro cell - pico cell (with a min. of 5MHz of BW by cell)  The macro cell has radius from 1Km to 35Km and they are destined to offer rural cover and highways for vehicles or other objects that move at high speed (114kbps-data transmission).  The micro cell has radius from 50m to 1Km. this offers services to fixed users or who and they move slowly with high density of traffic (urban) with 384 kbps speeds.  The pico cells has radius until 50m. Offer located cover and interior cover(stationary), with speeds of the order of the 2Mbps.
  53. 53. ASRao 3G CDMA2000 • EVDO Rel 0 (Evolution-Data Optimized or Evolution-Data only Release 0) • Data rates: – Forward link - 2.4Mbps. – Reverse link - 153kbps. • Encoding technique: – Forward link – 16QAM. – Reverse link - BPSK.
  54. 54. ASRao • Channel bandwidth of 1.25 MHz per radio channel • The first CDMA interface cdma2000 1xRTT means that a single 1.25 MHz radio channel is used. • cdma2000 1X supports an instantaneous data rate upto 307 kbps with typical throughput rate of 144kbps. • cdma2000 1xEV : Evolutionary advancement for CDMA • cdma2000 1xEV-DO: CDMA carriers with the option of Data Only radio channels • cdma2000 1xEV-DV: carriers with Data and Voice and can offer usable data rates up to 144 kbps with about twice as many voice channels as IS-95B.
  55. 55. ASRao The cdma2000 3xRTT standard uses three adjacent 1.25 MHz radio channels that are used together to provide instantaneous packet data throughput speeds in excess of 2 Mbps per user, although actual throughput depends upon cell loading, vehicle speed, and propagation conditions.
  56. 56. ASRao 3G TD-SCDMA The China Academy of Telecommunications Technology (CATT) and Siemens Corporation jointly submitted an IMT-2000 3G standard proposal in 1998, based on Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). TD-SCDMA relies on the existing core GSM infrastructure and allows a 3G network to evolve through the addition of high data rate equipment at each GSM base station. Up to 384 kbps of packet data is provided to data users in TD-SCDMA A 5 millisecond frame is used in TD-SCDMA, and this frame is subdivided into seven time slots which are flexibly assigned to either a single high data rate user or several slower users. By using TDD, different time slots within a single frame on a single carrier frequency are used to provide both forward channel and reverse channel transmissions. For the case of asynchronous traffic demand, such as when a user downloads a file, the forward link will require more bandwidth than the reverse link, and thus more time slots will be dedicated to providing forward link traffic than for providing reverse link traffic.
  57. 57. ASRao Frequency-division duplexing (FDD) is a method for establishing a full-duplex communications link that uses two different radio frequencies for transmitter and receiver operation. The transmit direction and receive direction frequencies are separated by a defined frequency offset. In the microwave realm, the primary advantages of this approach are: •The full data capacity is always available in each direction because the send and receive functions are separated; •It offers very low latency since transmit and receive functions operate simultaneously and continuously; •It can be used in licensed and license-exempt bands; •Most licensed bands worldwide are based on FDD; and •Due to regulatory restrictions, FDD radios used in licensed bands are coordinated and protected from interference, though not immune to it. Disadvantages of the FDD approach to microwave communication are: •Complex to install. Any given path requires the availability of a pair of frequencies; if either frequency in the pair is unavailable, then it may not be possible to deploy the system in that band; •Radios require pre-configured channel pairs, making sparing complex; •Any traffic allocation other than a 50:50 split between transmit and receive yields inefficient use of one of the two paired frequencies, lowering spectral efficiency; and •Collocation of multiple radios is difficult.
  58. 58. ASRao Time-division duplexing (TDD) is a method for emulating full-duplex communication over a half-duplex communication link. The transmitter and receiver both use the same frequency but transmit and receive traffic is switched in time. Advantages of this approach as it applies to microwave communication are: •It is more spectrum friendly, allowing the use of only a single frequency for operation and dramatically increasing spectrum utilization, especially in license-exempt or narrow-bandwidth frequency bands ; •It allows for the variable allocation of throughput between the transmit and receive directions, making it well suited to applications with asymmetric traffic requirements, such as video surveillance, broadcast and Internet browsing; •Radios can be tuned for operation anywhere in a band and can be used at either end of the link. As a consequence, only a single spare is required to serve both ends of a link. Disadvantages of traditional TDD approach to microwave communications are: •The switch from transmit to receive incurs a delay that causes traditional TDD systems to have greater inherent latency than FDD systems; •Traditional TDD approaches yield poor TDM performance due to latency; •For symmetric traffic (50:50), TDD is less spectrally efficient than FDD, due to the switching time between transmit and receive; and •Multiple co-located radios may interfere with one another unless they are synchronized.
  59. 59. ASRao HSDPA HSUPA 3.5G EVDO-Rev A EVDO-Rev B
  60. 60. ASRao HSPA • High Speed Packet Access is a collection of two mobile telephony protocols HSDPA and HSUPA. • High Speed Downlink Packet Access (HSDPA) – Data rates for Forward link - 14.4Mbps. – Encoding technique – QPSK and 16QAM • High Speed Uplink Packet Access (HSUPA) or EUL(Enhanced Uplink) – Data rates for Reverse link - 5.76Mbps. • Just a software update for most WCDMA networks.
  61. 61. ASRao HSPA+ • Evolved High Speed Packet Access (HSPA+) • Data rates: – Forward link - 42Mbps. – Reverse link - 22Mbps. • Encoding technique 64QAM.
  62. 62. ASRao EVDO Rev A • EVDO Rev A (Revision A) • Also called as EV-DV (Evolution Data/Voice) • Data rates: – Forward link - 3.1Mbps. – Reverse link - 1.8Mbps. • Encoding technique: – Forward link – 16QAM. – Reverse link - QPSK and 8PSK.
  63. 63. ASRao EVDO Rev B • Combine up to fifteen 1.25MHz carriers (20MHz) in forward and/or reverse link. Carriers not physically combined and not adjacent to each other. • Data rate: – Forward link = 3.1Mbps*15channels = 47Mbps. – Reverse link = 1.8Mbps*15channels = 27Mbps. • Encoding technique 64QAM. Uplink data rate increases from 3.1Mbps to 4.9Mbps per channel. Thus, Data rate: – Forward link = 4.9Mbps*15channels = 74Mbps. • Only software updation required.
  64. 64. Wireless Local Loop (WLL) and LMDs ASRao What is WLL? - WLL is a system that connects subscribers to the local telephone station wirelessly. •Unlike mobile cellular telephone systems, fixed wireless communication systems are able to take advantage of the very well-defined, time-invariant nature of the propagation channel between the fixed transmitter and fixed receiver. •Furthermore, modern fixed wireless systems are usually assigned microwave or millimeter radio frequencies in the 28 GHz band and higher, which is greater than ten times the carrier frequency of 3G terrestrial cellular telephone networks. •At these higher frequencies, the wavelengths are extremely small, which in turn allows very high gain directional antennas to be fabricated in small physical form factors. •At higher frequencies, too, more bandwidth can be easily used. •Fixed wireless networks at very high microwave frequencies are only viable where there are no obstructions, such as in a relatively flat suburban or rural setting.
  65. 65. ASRao Connection Setup UWLL WANU PSTN Trunk Switch function Transceiver WLL Controller Wireless Access Network Unit(WANU) – Interface between underlying telephone network and wireless link – consists of • Base Station Transceivers (BTS) • Radio Controller(RPCU) • Access Manager(AM) • Home Location Register(HLR) WASU Air AM Interface HLR TWLL Wireless Access Subscriber Unit(WASU) – located at the subscriber – translates wireless link into a traditional telephone connection
  66. 66. ASRao
  67. 67. ASRao •These services include the concept of Local Multipoint Distribution Service (LMDS), which provides broadband telecommunications access in the local exchange. •In 1998, 1300 MHz of unused spectrum in the 27 - 31 GHz band was auctioned by the US government to support LMDS. •The US LMDS band is 27.5 - 28.35 GHz, 29.1- 29.25 GHz, and 31.075 31.225 GHz. •One of the most promising applications for LMDS is in a local exchange carrier (LEC) network. •Unfortunately, finding a line-of-sight path is not the only requirement for maintaining a suitable fixed wireless connection for millimeter wave fixed wireless links. •Rain, snow, and hail can create large changes in the channel gain between transmitter and receiver.
  68. 68. ASRao Wireless LAN • In 1997 the FCC allocated 300 MHz of unlicensed spectrum in the Industrial Scientific and Medical (ISM) bands of 5.150 - 5.350 GHz and 5.725 - 5.825 GHz for the express purpose of supporting low-power license-free spread spectrum data communication. • This allocation is called Infrastructure (UNII) band. the Unlicensed National Information • By providing a license-free spectrum allocation, the FCC hoped to encourage competitive development of spread spectrum knowledge, spread spectrum equipment, and ownership of individual WLANs and other low power short range devices that could facilitate private computer communications in the workplace • Popularity of the Internet combined with wide scale acceptance of portable, laptop computers caused WLAN to become an important and rapidly growing segment.
  69. 69. ASRao • IEEE 802.11 was finally standardized in 1997 and provided interoperability standards for WLAN manufactures using 11 Mcps DS-SS spreading and 2 Mbps user data rates (with fallback to 1 Mbps in noisy conditions). • In 1999, the 802.11 High Rate standard (called IEEE 802.11b) was approved, thereby providing new user data rate capabilities of 11 Mbps, 5.5 Mbps in addition to the original 2 Mbps and 1 Mbps user rates of IEEE 802.11, which were retained.
  70. 70. ASRao • Both frequency hopping and direct sequence approaches were used in the original IEEE 802.11 standard ( 2 Mbps user throughput), but as of late 2001 only direct sequence spread spectrum (DS-SS) modems had thus far been standardized for high rate (11 Mbps) user data rates within IEEE 802.11. • The IEEE 802.11a standard provides up to 54 Mbps throughput in the 5 GHz band. • The DS-SS IEEE 802.11b standard has been named Wi-Fi • IEEE 802.11g is developing Complimentary Code Keying Orthogonal Frequency Division Multiplexing (CCK-OFDM) standards in both the 2.4 GHz (802.11b) and 5 GHz (802.11a) bands, and will support roaming capabilities and dual-band use for public WLAN networks, while supporting backward compatibility with 802.11b technology. • The frequency-hopping spread spectrum (FH-SS) proponents of IEEE 802.11 have formed the HomeRF standard that supports frequency hopping equipment.
  71. 71. ASRao • In 2001, HomeRF developed a 10 Mbps FH-SS standard called HomeRF 2.0. • It is worth nothing that both DS and FH types of WLANs must operate in the same unlicensed bands that contain cordless phones, baby monitors, Bluetooth devices, and other WLAN users. • The channelization scheme used by the network installer becomes very important for a high density WLAN installation, since neighboring access points must be separated from one another in frequency to avoid interference and significantly degraded performance. • User throughput performance changes radically when access points or clients are located near an interfering transmitter or when frequency planning is not carefully conducted.
  72. 72. ASRao • In mid 1990s, the High Performance Radio Local Area Network (HIPER-LAN) standard was developed to provide a similar capability to IEEE 802.11. • HIPERLAN was intended to provide individual wireless LANs for computer communications and used the 5.2 GHz and the 17.1 GHz frequency bands. • HIPERLAN provides asynchronous user data rates of between 1 to 20 Mbps, as well as time bounded messaging at rates of 64 kbps to 2.048 Mbps. HIPERLAN was designed to operate up to vehicle speeds of 35 km/hr, and typically provided 20 Mbps throughput at 50 m range. • In 1997, Europe‟s ETSI established a standardization committee for Broadband Radio Access Networks (BRANs). • The goal of BRAN is to develop a family of broadband WLAN-type protocols that allow user interoperability, covering both short range (e.g., WLAN) and long range (e.g., fixed wireless) networking.
  73. 73. ASRao • HIPERLAN/2 has emerged as the next generation European WLAN standard and will provide up to 54 Mbps of user data to a variety of networks, including the ATM backbone, IP based networks, and the UMTS core. • HIPERLAN/2 is anticipated to operate in the 5 GHz band. • Meanwhile, IEEE 802.11a is emerging as North America‟s next generation WLAN. • Like HIPERLAN/2, IEEE 802.11a supports up to 54 Mbps user data rate for integration into backbone ATM, UMTS, and IP networks and will operate in the 5.15 - 5.35 GHz ISM band. • Meanwhile, Japan‟s Multimedia Mobile Access Communication System (MMAC) has been developing high data rate ( 25Mbps) WLAN standards for use in the 5.15 5.35 GHz band.
  74. 74. ASRao Pros & Cons of 802.11 Pros.. •Mobility •Compatible with IP networks •High speed data connectivity •Unlicensed frequencies •Highly secure •Easy and fast installation •Simplicity •Scalability •Very low cost Cons.. •Shared-medium technology – bandwidth limited by RF spectrum •Limited number of non overlapping channels •Multipath effects indoor •Interference in the 2.4 GHz and 5 GHz bands •Limited QoS •Power control •High overhead MAC protocol
  75. 75. ASRao Protocol 802.11 Release year Freq. (GHz) Thru. (Mbps Data (Mbps) - 1997 2.4 00.9 002 a 1999 5 23 054 b 1999 2.4 04.3 g 2003 2.4 n 2009 y 2008 Mod. Rin Riout (m) (m) ~20 ~100 OFDM ~35 ~120 011 DSSS ~38 ~140 19 054 OFDM ~38 ~140 2.4, 5 74 248 ~70 ~250 3.7 23 054 ~50 ~5000
  76. 76. ASRao •802.11a was the first wireless networking standard, but 802.11b was the first widely accepted one, followed by 802.11g and 802.11n. •802.11b and 802.11g use the 2.4GHz ISM band, because of this choice of frequency band, 802.11b and g equipment may occasionally suffer interference from microwave ovens and cordless phones. •Bluetooth devices, while operating in the same band, in theory do not interfere with 802.11 b/g because they use a frequency hopping spread spectrum signaling method (FHSS) while 802.11 b/g uses a DSSS. •802.11 a uses the 5GHz UNII band, which offers 8 non-overlapping channels rather than the 3 offered in the 2.4GHz ISM frequency band. •802.11 a (5GHz) , this high carrier frequency brings a slight disadvantage: the effective overall range of 802.11a is slightly less than that of 802.11 b/g; 802.11 a signals cannot penetrate as far as those for 802.11 b because they absorbed more readily by walls and other solid objects in their path. •802.11 b devices suffer interference from other products operating in the 2.4GHz band. Devices operating in the 2.4GHz range include: microwave ovens, Bluetooth devices, baby monitors and cordless telephones. •802.11g hardware is fully backwards compatible with 802.11 b hardware.
  77. 77. ASRao •802.11 d is enhancement to 802.11 a and b that allows for global roaming. •802.11 e enhancement to 802.11 that includes QoS. •802.11 h enhancement to 802.11 a that resolves interference issues. •802.11 i enhancement to 802.11 that offers additional security for WLAN applications, which defines more robust encryption and authentication.
  78. 78. ASRao Personal Area Network (PAN) • RFID - Very short range (10 meters) sensor technology used to supplement bar-code reader type applications • Infrared - Short range, usually line-of-sight, non-RF technology, - used mostly for wireless remote control, or wire replacement applications • Zig bee -Very low power (and low speed) short distance (10m) transmission standard -Operates in 868-918 KHz, and 2.4GHz bands using 802.15.4 PAN standards
  79. 79. ASRao Personal Area Network (PAN) Bluetooth
  80. 80. ASRao Bluetooth @ Home NO WIRES Digital Camera Computer Scanner Inkjet Printer xDSL Access Point Home Audio System MP3 Player PDA Cell Phone Cordless Phone Base Station
  81. 81. ASRao •Bluetooth operates in the 2.4 GHz ISM Band ( 2400 2483.5 MHz) and uses a frequency hopping TDD scheme for each radio channel. •Each Bluetooth radio channel has a 1 MHz bandwidth and hops at a rate of approximately 1600 hops per second. •Transmissions are performed in 625 microsecond slots with a single packet transmitted over a single slot. •For long data transmissions, particular users may occupy multiple slots using the same transmission frequency, thus slowing the instantaneous hopping rate to below 1600 hops/second. •The frequency hopping scheme of each Bluetooth user is determined from a cyclic code of length 227 - 1, and each user has a channel symbol rate of 1 Mbps using GFSK modulation. •The standard has been designed to support operation in very high interference levels and relies on a number of forward error control (FEC) coding and automatic repeat request (ARQ) schemes to support a raw channel bit error rate (BER) of about 10-3 . •Different countries have allocated various channels for Bluetooth operation.
  82. 82. ASRao •Audio, text, data, and even video is contemplated in the Bluetooth standard. •The IEEE 802.15 standards committee has been formed to provide an international forum for developing Bluetooth and other PANs that interconnect pocket PCs, personal digital assistants (PDAs), cell phones, light projectors, and other appliances Fig: Example of a Personal Area Network (PAN) as provided by the Bluetooth standard.
  83. 83. ASRao Bluetooth system is based on a low cost, short range radio-link which enables devices to communicate wirelessly via short range radio link. The Bluetooth is a universal radio interface on the Globally 2.4 GHz frequency band facilitating wireless communication of data and voice in stationary and mobile environments. This chip is tiny, low-power consuming and can be easily imbedded in existing electronic devices. These devices can form a quick ad-hoc secure “piconet” and start communication. Connections in the “piconets” can occur even when mobile.
  84. 84. Strength of Bluetooth Cheap Initial costs $ 20 ASRao Future target $ 5 Tiny It is only 10.2 *14* 1.6 mm. Easy implementation. low-power consumption - Bluetooth radio consumes less than 3% of the power compared to that of modern mobile phone. It works all over the world - Operates on ISM radio band, Unlicensed band. Supports point-to-point & point-to-multi-point communication. High Security interference. - It allows authentication & encryption - Protection against High speed - Current speed up to 1 Mbps (723.2 Kbps)
  85. 85. ASRao A collection of devices connected via Bluetooth technology in an ad hoc fashion. • A piconet starts with two connected devices, and may grow to eight connected devices. • All Bluetooth devices are peer units and have identical implementations. However, when establishing a piconet, one unit will act as a Master and the other(s) as slave(s) for the duration of the piconet connection. • Spread-Spectrum frequency hopping • • • • A device will use 79 individual randomly chosen frequencies within a designated range, changing from one to another on a regular basis. The designated range is from 2.402GHz to 2.480GHz, in steps of 1MHz. The frequency hopping is done at a rate of 1600 times a second. This allows more devices to use the limited time slice and secondly reduces the chance of two transmitters being on the same frequency at the same time.
  86. 86. ASRao • Ad hoc client/server topology, 8 active & up to 256 parked devices per piconet. • 1 master per piconet “speaking” to slaves via TDM. • Multiple piconets up to 13 per scatternet.
  87. 87. ASRao
  88. 88. ASRao Summary G 1 2 2.5 3 3.5 4 Technology Data Rates Analog Typical 2.4 Kbps; max 22 Kbps Digital – TDMA, CDMA 9.6 - 14.4 Kbps (circuit data) GPRS – mux packets in voice timeslots 15 - 40 Kbps Improved modulation, using CDMA variants 50 – 144 Kbps (1xRTT); 200 – 384 Kbps (UMTS); 500 Kbps – 2.4 Mbps (EVDO) More modulation tweaks 2–14 Mbps (HSPA) New modulation (OFDMA); Multi-path (MIMO); All IP LTE: >10 Mbps; eventual potential >100 Mbps