Lecture #2

A Tale of Two Technologies: WiMAX vs. LTE

Dr. Kun Yang University of Essex, UK

17th March 2009 @ NII

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Agenda

Wireless LAN (Local Area Networks) Wireless MAN: WiMAX Mobile Cellular Systems 3GPP LTE (Long Term Evolution) Femto Cell and Mobility Q&A

Some slides here pay courtesy to J. He, & D. Hunter.

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1 IEEE 802 (LAN) vs OSI

‰ IEEE 802 reference model ‰ Lower layers of OSI model ƒ Physical ƒ Media access control (MAC) ƒ Logical link control (LLC)

•IEEE 802. 11 •IEEE 802.15 •IEEE 802.16 •IEEE 802.21

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IEEE 802.11 Version Summary

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2 Comparison: infrastructure vs. ad-hoc networks

infrastructure network

AP: Access Point AP

AP wired network AP

ad-hoc network

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802.11 - Architecture of an infrastructure network 802.11 LAN 802.x LAN Station (STA) ƒ terminal with access mechanisms STA1 to the wireless medium and radio contact to the access point BSS1 Basic Service Set (BSS) Access Portal Point ƒ group of stations using the same radio frequency Distribution System Access Point Access ESS Point ƒ station integrated into the wireless LAN and the distribution system

BSS2 Portal ƒ bridge to other (wired) networks Distribution System

STA2 802.11 LAN STA3 ƒ interconnection network to form one logical network (EES: Extended Service Set) based on several BSS 6

3 802.11 - Architecture of an ad-hoc network

802.11 LAN Direct communication within a limited range STA1 STA BSS1 3 ƒ Station (STA): terminal with access mechanisms to the

STA2 wireless medium ƒ Basic Service Set (BSS): group of stations using the same radio frequency BSS2

STA5

STA4 802.11 LAN

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ETSI - HIPERLAN

ETSI standard ƒ European standard, cf. GSM, DECT, ... ƒ Enhancement of local Networks and interworking with fixed networks ƒ integration of time-sensitive services from the early beginning HIPERLAN family ƒ one standard cannot satisfy all requirements • range, bandwidth, QoS support • commercial constraints ƒ HIPERLAN 1 standardized since 1996

higher layers

medium access logical link network layer control layer control layer channel access medium access data link layer control layer control layer

physical layer physical layer physical layer

HIPERLAN layers OSI layers IEEE 802.x layers

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4 802.11 - MAC layer I - DFWMAC

Traffic services ƒ Asynchronous Data Service (mandatory) • exchange of data packets based on “best-effort” • support of broad cast and mul ti cast ƒ Time-Bounded Service (optional) • implemented using PCF (Point Coordination Function) Access methods ƒ DFWMAC-DCF CSMA/CA (mandatory) • collision avoidance via randomized „back-off“ mechanism • minimum distance between consecutive packets • ACK packet for acknowledgements (not for broadcasts) ƒ DFWMAC-DCF w/ RTS/CTS (optional) • Distributed Foundation Wireless MAC • avoids hidden terminal problem ƒ DFWMAC- PCF (optional) • access point polls terminals according to a list 9

802.11 - MAC layer II Priorities ƒ defined through different inter frame spaces (IFS) ƒ no guaranteed, hard priorities ƒ SIFS (Short Int er Frame Spaci ng) ) • highest priority, for ACK, CTS, polling response ƒ PIFS (PCF IFS) • medium priority, for time-bounded service using PCF ƒ DIFS (DCF, Distributed Coordination Function IFS) • lowest priority, for asynchronous data service

DIFS DIFS PIFS SIFS medium busy contention next frame t direct access if medium is free ≥ DIFS

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5 802.11 - CSMA/CA access method I

contention window DIFS DIFS (randomized back-off mechanism)

medium busy next frame

direct access if t medium is free ≥ DIFS slot time ƒ station ready to send starts sensing the medium (Carrier Sense based on CCA, Clear Channel Assessment) ƒ if the medium is free for the duration of an Inter-Frame Spp()ace (IFS), the station can start sendingg(p (IFS depends on service type) ƒ if the medium is busy, the station has to wait for a free IFS, then the station must additionally wait a random back-off time (collision avoidance, multiple of slot-time) ƒ if another station occupies the medium during the back-off time of the station, the back-off timer stops (fairness) 11

802.11 - competing stations - simple version

DIFS DIFS DIFS DIFS

boe bor boe bor boe busy station1

boe busy station2

busy station3

boe busy boe bor station4

boe bor boe busy boe bor sttitation 5 t

medium not idle (frame, ack etc.) busy boe elapsed backoff time

packet arrival at MAC bor residual backoff time

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6 802.11 - CSMA/CA access method II Sending unicast packets ƒ station has to wait for DIFS before sending data ƒ receivers acknowledgg(e at once (after waiting g) for SIFS) if the packet was received correctly (CRC) ƒ automatic retransmission of data packets in case of transmission errors

DIFS data sender SIFS ACK receiver DIFS other data stations t waiting time contention

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802.11 - DFWMAC

Sending unicast packets ƒ station can send RTS with reservation parameter after waiting for DIFS (reservation determines amount of time the data packet needs the medium) ƒ acknowledgement via CTS after SIFS by receiver (if ready to receive) ƒ sender can now send data at once, acknowledgement via ACK ƒ other stations store medium reservations distributed via RTS and CTS

DIFS RTS data sender SIFS SIFS CTS SIFS ACK receiver

NAV (RTS) DIFS other NAV (CTS) data stations t defer access contention

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7 Fragmentation

DIFS RTS frag frag sender 1 2 SIFS SIFS SIFS CTS SIFS ACK SIFS ACK receiver 1 2

NAV (RTS) NAV (CTS) NAV (frag ) DIFS 1 data other NAV (ACK1) stations t contention

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DFWMAC-PCF I

t t 0 1 SuperFrame

medium busy PIFS SIFS SIFS D D point 1 2 coordinator SIFS SIFS U U wireless 1 2 stations stations‘ NAV NAV

At the beginning of the contention-free period, the AP transmits a beacon frame (not shown above –see later) ƒ This announces the maximum duration of the contention-free period ƒ All stations use this duration to set their NAVs

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8 DFWMAC-PCF II

t2 t3 t4

PIFS SIFS D D CF point 3 4 end coordinator SIFS U wireless 4 stations stations‘ NAV NAV contention free period contention t period

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802.11 - Frame format Types ƒ control frames, management frames, data frames Sequence numbers ƒ important against duplicated frames due to lost ACKs Addresses ƒ receiver, transmitter (physical), BSS identifier, sender (logical) Miscellaneous ƒ sending time, checksum, frame control, data bytes 2 266624 60-2312 Frame Duration Address Address Address Sequence Address Data CRC Control ID 1 2 3 Control 4

version, type, fragmentation, security, ...

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9 MAC address format scenario to DS from address 1 address 2 address 3 address 4 DS ad-hoc network 0 0 DA SA BSSID - ifinfras truc ture 0 1 DA BSSID SA - network, from AP infrastructure 1 0 BSSID SA DA - network, to AP infrastructure 1 1 RA TA DA SA network, within DS

DS: Distribution System AP: Access Point DA: Destination Address SA: Source Address BSSID: Basic Service Set Identifier RA: Receiver Address TA: Transmitter Address

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802.11 - MAC management

Synchronization ƒ try to find a LAN, try to stay within a LAN ƒ timer etc. Power management ƒ sleep-mode without missing a message ƒ periodic sleep, frame buffering, traffic measurements Association/Reassociation ƒ integration into a LAN ƒ roaming, i.e. change networks by changing access points ƒ scanning, i.e. active search for a network MIB - Management Information Base ƒ managing, read, write

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10 A bit info on MANET (Mobile Ad hoc Networks) ….

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MANET Introduction Mobile ad hoc networks (MANETs) are basically peer-to-peer multihop mobile wireless networks that ƒ have neither fixed communication infrastructure ƒ nor any base stations (BSs). Control is more complex due to its ad hoc nature and mobility. ƒ Unlike the typical Internet, which has dedicated nodes for basic network operations such as authorization, routing, packet forwarding, and network management, all these functions should be performed by all MNs themselves in MANETs. Efficient routing of packets is a primary MANET challenge. MA NET s use m ul tih op rat h er th an sin gl e-hop routin g to delive r packets to their destination.

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11 Routing Conventional networks typically rely on distance-vector or link- state algorithms, which depend on periodic broadcast advertisements of all routers to keep routing tables up-to-date. In some cases, MANETs also use these alithlgorithms, whihhich ensure that the route to every host is always known. However, this approach presents several problems: ƒ periodically updating the network topology increases bandwidth overhead; ƒ repeatedly awakening hosts to receive and send information quickly exhausts batteries; ƒ the propagation of routing information, which depends on the number of existing hosts, causes overloading, thereby reducing scalability; ƒ redundant routes accumulate needlessly; ƒ communication systems often cannot respond to dynamic changes in the network topology quickly enough.

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On-demand Routing Algorithms

Rather than relying on periodical broadcasts of available routes, called proactive, a re-active algorithm discovers routes is needed. Because the route to every mobile node is not known at any given time, these algorithms must build and maintain routes. Two representative MANET re-active algorithms: ƒ DSR: data source routing ƒ AODV: ad-hoc distance vector

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12 Bluetooth

Why Bluetooth ƒ 1994 – Ericsson study on a wireless technology to link mobile phones and accessories ƒ Lets replace all those ugly wires with a short range low data rate wireless system. ƒ Basically to standardise wireless keyboards and mice • And add a few more on the way

Main references: ƒ IEEE Std 802.15.1, “Information Technology — Telecommunications and Information Exchange between Systems — Local and Metropolitan Area Networks — Specific Requirements Part 15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Wireless Personal Area Networks (WPANs),” 2002.

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Bluetooth

Bluetooth is a standard for wireless communications. Bluetooth is an infrastructure less short-range wireless system intenddded to repl ace th e cabl blbe between el ectronic user terminals with RF links. The devices can also be used for communications between portable computers, act as bridges between other networks, or serve as nodes of ad hoc networks. This range of applications is known as wireless personal area network (WPAN). Bluetooth devices use the 2.4 GHz band, which is unlicensed in most countries.

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13 Piconet

The Bluetooth topology is a star network where a master node can have up to seven slave nodes wirelessly connected to it to form a piconet. Picone t is the si mpl est config fiurati on of a Blue too th ne twor k. Each piconet uses a centrally assigned time-division multiple access (TDMA) schedule and frequency hopping pattern. Transmission power is typically around 20 dBm and the transmission range is on the order of tens of meters.

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Scatternet Piconets may be connected together, thus forming a scatternet. A scatternet supports multihop. ƒ i.e., two nodes can communicate with each other even if there is no direct connection between them by using other nodes as relays. Two piconets can communicate by means of a common node belonging to both of them. A node can be a master in one piconet at most and a slave in several others.

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14 Bluetooth vs. IEEE 802.11 (1)

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Bluetooth vs. IEEE 802.11 (2)

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15 Agenda

Wireless LAN (Local Area Networks) Wireless MAN: WiMAX (IEEE 802.16) ƒ WiMAX PHY/MAC/QoS Features ƒ Comparison with IEEE 802.11 Mobile Cellular Systems 3GPP LTE (Long Term Evolution) Femto Cell and Mobility Q&A

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IEEE 802.16

WiMAX is the commercialization of the IEEE 802.16 standard, ƒ Started at the National Institute of Standards and Technologies (NIST) in 1998 and then transferred to the IEEE to form Working Group 802.16. ƒ In June 2004, thkhe working group won approvallfhl for the latest 802.16 standard for fixed wireless access, known as IEEE 802.16-2004. ƒ In December 2005, an extension that addresses mobility also won approval as IEEE 802.16e-2005. Specifies the air interface, including the medium access control layer (MAC) and physical layer (PHY), of fixed point-to-multipoint (PMP) and Mesh broadband wireless access systems providing multiple services. The standard includes a particular physical layer specification broadly applicable to systems operating between 10 and 66 GHz, and below 10GHz.

WiMAX: Worldwide Inter-operability for Microwave Access 32

16 The WiMAX Forum

Comprises a group of industry leaders (Intel, AT&T, Samsung, Motorola, Cisco, and others), has closely supported and promoted the technology. The group’s workforce is divided along multiple working groups that focus on technical, regulatory, and marketing aspects. Loads of live discussion about technical details of WiMAX and its simulation and implementation.

High Performance Radio Metropolitan Area Network (HiperMAN))p, the European Telecommunications Standards Institute’s MAN standard, share the same physical layer (PHY) and medium access control (MAC) layer specifications.

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Standard History •First standard based on proprietary implementations of DOCSIS/HFC architecture in wireless domain

802.16 • Original fixed wireless broadband air Interface for 10 –66 (Dec 2001) GHz: Line‐of‐sight only, Point‐to‐Multi‐Point applications

802.16c • 802.16 Amendment WiMAX System Profiles 10 ‐ 66 GHz, (2002) line‐of‐sight

• 802.16a Extension for 2‐11 GHz: Targeted for non‐line‐of‐sight, Point‐to‐Multi‐Point applications like “last mile” (Jan 2003) broadband access

802.16d (802.16-2004) • Adds WiMAX System Profiles and Errata for 2‐11 GHz (Oct 2004)

802.16e • MAC/PHY Enhancements to support subscribers (802.16-2005) moving at vehicular speeds (Dec 2005) 34

17 Other versions

802.16f-2005 — Management Information Base (MIB) 802.16g-2007 — Management Plane Procedures and Services 802. 16k-2007 — Bridging of 802.16 (an amendment to 802.1D) 802.16h — Improved Coexistence Mechanisms for License-Exempt Operation 802.16i — Mobile Management Information Base 802.16j — Multihop Relay Specification 802.16Rev2 — Consolidate 802.16-2004, 802.16e, 802.16f, 802.16g and possibly 802.16i into a new document. 802.16m — Advanced Air Interface. Data rates of 100 Mbit/s for mobile applications and 1 Gbit/s for fixed applications.

Source: wikipedia

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Services

Deliver both fixed and mobile wireless broadband services Two forms of wireless service: ƒ Desirable Non-line-of-sight (NLOS) service • Small antenna • 2 – 11 GHz • Up to 8 km radius (cell phone zone) ƒ Line-of-sight (LOS) • Fixed antenna; strong and stable connection • 10 – 66 GHz • Up to 50 km radius Applications ƒ BdbdBroadband on-dddemand • Fast deployment of WLAN hotspots ƒ Residential broadband • Hard competition with DSL, cable and fiber ƒ Cellular Backhaul ƒ Underserved areas ƒ Emergency communication systems 36

18 Reference Model

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Protocol Stack

Upper Layers

Service specific convergence sublayer Data Link MAC sublayer common part Layer Security sublayer Transmission convergence sublayer

Physical Physical medium dependent sublayer Layer (QPSK | QAM-16 | QAM-64)

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19 PHY Considerations

Broadband channels ƒ Wide channels (()20, 25, or 28 MHz) ƒ High capacity – Downlink AND Uplink Multiple access ƒ TDM/TDMA ƒ High rate burst modems Adaptive burst profiles on uplink and downlink Duplex scheme ƒ Time-Division Duplex (TDD) ƒ Frequency-Division Duplex (FDD) [including Burst FDD] Support for half-duplex terminals (cheaper)

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Adaptive PHY

Channel Symbol Bitrate (Mbit/s) Num. of PSs Width Rate QPSK 16- 64-QAM (Phy. slots) (MHz) (Msym /s ) QAM (1ms frame) 20 16 32 64 96 4000 25 20 40 80 120 5000 28 22.4 44.8 89.6 134.4 5600 40

20 Adaptive Burst Profiles

Burst profile ƒ Set of parameters that describe the uplink or downlink transmission properties associated with an interval usage code (IUC) ƒ Each profile contains parameters such as modulation type, forward error correction (FEC) type, preamble length, guard time, etc. Dynamically assigned according to link conditions ƒ Burst by burst, per subscriber station ƒ Trade-off between cappyacity vs. robustness in real time Burst profile for downlink broadcast channel is well known ƒ All other burst profiles could be configured “on the fly”

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TDD Frame

Frame duration: 1 ms Physical Slot (PS) = 4 symbols

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21 TDD Downlink Subframe

DIUC: Downlink Interval Usage Code TTG: Transmit Transition Gap 43

Burst FDD Frame

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22 FDD Downlink Subframe

TDMA portion: transmits data to some half-duplex SSs (the ones scheduled to transmit earlier in the frame than they receive). Need preamble to re- sync (carrier phase) 45

Typical Uplink Subframe (TDD or FDD)

SSTG : Subscriber Station Transition Gap UIUC: Uplink Interval Usage Code

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23 Air Interfaces Specifications

Designation Applicability MAC Duplexing WirelessMAN-SC 10-66 GHz Basic TDD, FDD, Licensed HFDD WirelessMAN-SCa 2-11 GHz Basic, (ARQ), TDD, FDD Licensed (STC), (AAS) 2-11 GHz Basic, (ARQ), TDD, FDD Licensed (STC), (AAS) WirelessMAN- OFDM 2-11 GHz License- Basic, (ARQ), TDD exempt (STC), (DFS), (MSH), (AAS) 2-11 GHz Basic, (ARQ), TDD, FDD Licensed (STC), (AAS) WirelessMAN- OFDMA 2-11 GHz License- Basic, (ARQ), TDD exempt (STC), (DFS), (MSH), (AAS)

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MAC Requirements

Provide Network Access Address the Wireless environment ƒ e.g., very efficient use of spectrum Broadband services ƒ Very high bit rates, downlink and uplink ƒ A range of QoS requirements ƒ Convergence layers to ATM, IP, Ethernet, ... Likelihood of terminal being shared ƒ Base Station may be heavily loaded Security Support PHY alternatives ƒ Adaptive mod, TDD/FDD; single-carrier, OFDM/OFDMA, etc.

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24 MAC layer architecture

IP/Ethernet/VLAN ATM Packet convergence sub‐layer ATM convergence sub‐layer MAC (classify, connection, QoS, (classify, connection, QoS, Layer bandwidth allocation) bandwidth allocation)

Basic Primary Secondary Other connects connection connection Traffic connection (Initial access (RLC and short, (authentication, connection (DHCP, TFTP, Broadcast Time‐critical Connection (data) SNMP..) Multicast) MAC msg) setup) Fragmentation Packing Grant management subheader Mesh subheader Management connections subheader subheader MAC (Gener ic or bdidthbandwidth request) HdHeader (6 btbytes= 48 bits ) Basic connection: short, time-urgent msg Transmission Convergence sub‐layer Primary connection: Long, delay-tolerantPHY msg10‐66 GHz PHY 2‐11 GHz Secondary connection: Delay-tolerant standard-based msg

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QoS Support

QoS support is critical for the support of commercial applications Deflffines 4+1 class of services, associated dh with connections – ref. next slide Scheduling Services Parameters ƒ Maximum sustained traffic rate ƒ Minimum reserved traffic rate ƒ Maximum latency ƒ Tolerated jitter ƒ Traffic priority ƒ Request/transmission policy Bandwidth request and grant mechanisms

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25 Classes of Service

Unsolicited Grant Services (UGS) ƒ for constant bit-rate (CBR) or CBR-like service flows (SFs), e.g. T1/E1 Real-time Polling Services (rtPS) ƒ for rt-VBR-like SFs such as MPEG video Non-real-time Polling Services (nrtPS) ƒ for nrt SFs with better than best effort service such as bandwidth- intensive file transfer Best Effor t (BE) ƒ for best-effort traffic

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Mandatory QoS service flow parameters

ƒ Maximum sustained traffic rate (MSTR) ƒ Minimum reserved traffic rate (MRTR) ƒ Maximum latency (ML) ƒ Tolerated jitter (TJ) ƒ Traffic priority (TP) ƒ Request/transmission policy (RTP)

Service MSTR MRTR ML TJ TP RTP

UGS Yes Optional Yes Yes No Yes rtPS Yes Yes Yes No No Yes nrtPs Yes Yes No No Yes Yes

BE No No No No Yes Yes

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26 Bandwidth Request and Allocation SSs make bandwidth requests to the BS in many ways: ƒ Implicit requests (UGS): No actual messages, negotiated at connection setup ƒ Send a standalone MAC message called ”BW request” in an allready granted slot (allocated via polling service). ƒ Use the ”contention request opportunities” interval, e.g., upon being polled by the BS (multicast or broadcast poll). ƒ Piggyback a BW request message on a data packet. BS grants/allocates bandwidth in one of two modes: ƒ Grant Per Subscriber Station (GPSS) ƒ Grant Per Connection (GPC) Decision based on requested bandwidth and QoS requirements vs the available resources at BS. Grants are realized through the UL-MAP.

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Unicast Polling

BS SS 1. BS allocates space for the SS in the uplink subframe (using UL- Poll MAP) Request 2. SS uses the allocated space to Allocate send a bw request. Data 3. BS allocates the requested space for the SS if available ((gusing UL- MAP 4. SS uses allocated space to send scheduling data.

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27 Agenda

Wireless LAN (Local Area Networks) Wireless MAN: WiMAX (IEEE 802.16) ƒ WiMAX PHY/MAC Features ƒ Comparison with IEEE 802.11 Mobile Cellular Systems 3GPP LTE (Long Term Evolution) Femto cell and Mobility Q&A

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802.11 vs. 802.16: Spectrum

UNII

International International US Japan ISM Licensed ISM Licensed Licensed Licensed

802.16

802.11

1 2 3 4 5 GHz

802.16a has both licensed and license-exempt options

ISM: Industrial, Scientific & Medical Band – Unlicensed band U-NII: Unlicensed National Information Infrastructure – Unlicensed band, by FCC, mainly for 802.11a. J. Orr of Proxim 56

28 Channel Performance

Channel Maximum Maximum Bandwidth Data Rate bps/Hz

802.11a 20 MHz 54 Mbps ~2.7 bps/Hz

10, 20 MHz; 802.16a 1.75, 3.5, 7, 14 MHz; 63 Mbps ~5.0 bps/Hz 3, 6 MHz

Scalability: 802. 11a MAC des iigne d to support 10’s o f users wh ereas 802.16 to support thousands of users

802.16 is designed for metropolitan performance

J. Orr of Proxim 57

QoS

IEEE 802.11 IEEE 802.16a

ƒ Contention-based MAC ƒ Grant-request MAC (CSMA/CA) => poor ƒ QoS mechanism is part of the performance under heavy load. standard ƒ No guaranteed QoS ƒ Designed to support Voice ƒ No differentiated service and Video on a per-user basis QoS ƒ Supports 5 ƒ TDD only – asymmetric differentiated service ƒ 802. 11e: Qo S is pr ior itiza tion levels only ƒ TDD/FDD – asymmetric or symmetric ƒ AMC: Adaptive Modulation and Coding

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29 Range 802.11 802.16a Optimized for ~100 meters Optimized for up to 50 Km

No “near-far” compensation Designed to handle many users spread out over kilometers

Designed to handle indoor multi-path Designed to tolerate greater (delay spread of 0.8μ seconds), multi-path delay spread up to 10.0μ seconds, optimized for indoor optimized for outdoor NLOS performance

Optimization centers around PHY PHY and MAC ddiesigned with multi -mile range and MAC layer for 100m range in mind

Range can be extended by increasing trans. Power - may be non-standard Standard MAC

802.16a is designed for distance 59

IEEE 802.11 vs 802.16: Summary

802.11 and 802.16 both gain broader industry acceptance through conformance and interoperability by multiple vendors

802.16 complements 802.11 by creating a complete MAN-LAN solution

• 802.11 is mainly optimized for license-exempt LAN operation • 802. 16 is ma in ly op tim ize d for licensed MAN operation.

J. Orr of Proxim 60

30 Agenda

Wireless LAN (Local Area Networks) Wireless MAN: WiMAX (IEEE 802.16) Mobile Cellular Systems 3GPP LTE (Long Term Evolution) Femto cell and Mobility Q&A

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Motivation

Radio spectrum is very limited, ƒ we have only 10-25MHz dedicated to wireless communication. Suchbddhllh narrow bandwidth allows 100-400 chlfhannels of reasonable quality, ƒ which is not rational and commercially not profitable to develop network for such small number of mobile subscribers. Then the cellular idea: division of the whole geographical area to relatively small cells, and each cell mamay reuse the same frequencies bby reducing power of transmission. Each cell has its own antenna (base station), and all base stations are interconnected using microwave or cable communication. 62

31 A bit of history Once upon a time there was analog cellular communication ƒ didn’t support encryp tion, com pression, and ISDN compatibility; ƒ in addition each country (company) developed its own system, which was incompatible with everyone else’s in equipment and operation. So, in early 80s Europeans realized that pan-European public mobile system should be developed. The new system had to meet certain criteria: ƒ Good subjective speech quality ƒ Low terminal and service cost ƒ International roaming ƒ ISDN compatibility ƒ Digital 63

Cellular Network Organization

Areas divided into cells ƒ Each cell served by its own base station consisting of transmitter, receiver, and control unit, ƒ Cells set up such that antennas of all neighbors are equidistant (hexagonal pattern)

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32 Frequency Reuse

Adjacent cells are assigned different frequencies to avoid interference or crosstalk Obfbbjective is to reuse frequency in nearby celllls ƒ 10 to 50 frequencies assigned to each cell ƒ Transmission power controlled to limit power at that frequency escaping to adjacent cells. ƒ The issue is to determine how many cells must intervene between two cells using the same frequency.

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Examples

N=4 N=7

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33 Frequency reuse

Reuse Distance (D): minimum distance between centres of cells that use the same band of frequencies (co-channels)

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Increasing Capacity

Adding new channels Frequency borrowing – frequencies are taken from adllbdlldjacent cells by congested cells Cell splitting – cells in areas of high usage can be split into smaller cells Cell sectoring – cells are divided into a number of wedge-shaped sectors, each with their own set of channels. Directional Antennas must be used in this case. Microcells – a decrease in cell size results in a reduction of the radiated power levels.

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34 Example: Microcells

Area: 213 km2 , Bandwidth: 336 channels per cluster, cells per cluster: N=7 ƒ Number of channels per cell is 336/7=48 If cell radius R=1.6 km, then 32 total cells ƒ Total channel capacity is 48 x 32 = 1536 If cell radius R=0.6 km, then 128 cells ƒ Total channel capacity is 48 x128 =6144 channels

Total cells: 32 Total cells: 128 69

Architecture of the GSM system

GSM is a PLMN (Public Land Mobile Network) ƒ several providers setup mobile networks following the GSM standard within each country ƒ components • MS (mobile station) • BS (base station) • MSC (mobile switching center) • LR (location register) ƒ subsystems • RSS (radio subsystem): covers all radio aspects • NSS (network and switching subsystem): call forwarding, handover, switching • OSS (operation subsystem): management of the network

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35 GSM: overview

OMC, EIR, AUC HLR GMSC NSS fixed network with OSS

VLR MSC MSC VLR

BSC

BSC

RSS

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GSM: system architecture

radio network and fixed subsystem switching subsystem partner networks

MS MS ISDN PSTN MSC Um

BTS Abis BSC BTS EIR

SS7 HLR

BTS VLR BSC ISDN BTS MSC A PSTN BSS IWF PSPDN CSPDN 72

36 Agenda

Wireless LAN (Local Area Networks) Wireless MAN: WiMAX (IEEE 802.16) Mobile Cellular Systems 3GPP LTE (Long Term Evolution) Comparison and Mobility Q&A

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Cellular Networks: Generations

Once upon a time there was analog cellular communication – 1st G 2nd Generation (2G): digital, early 80s, GSM 2.5G or GPRS: 140.8 kb/s in theory, 56 kb/s in practice 2.75G or E-GPRS or EDGE (Enhanced Data Rates for GSM Evolution): 180 kbps effective 3G: ƒ UMTS using WCDMA supports 14Mbps in theory. 384 kbps, or 3.6 Mbps for HSDPA handsets; • O2, 3, Orange, AT&T, HK, Taiwan, etc. • Different countries use diff. frequencies, thus diff. handsets ƒ CDMA-2000: (2.5G+3G), e.g., China Unicom ƒ TD-SCDMA at China; to avoid patent fees 3.5G: UMTS is being upgraded to High Speed Downlink Packet Access (HSDPA): up to 7.2 Mb/s. 3.99G/4G: the 3GPP Long Term Evolution (LTE) project plans to move UMTS to 4G: 100 Mb/s downlink and 50 Mb/s uplink, using OFDM. 74

37 3GPP: 3rd Generation Partnership Project

Established in Dec. 1998, 3GPP is a collaboration between ggproups of telco associations from across the world, such as ETSI (Europe), ARIB/TTC (Japan), China, North America, South Korea, etc. Its aim it to make a globally applicable 3G mobile phone system specification within the scope of the ITU’s International Mobile Telecommunications (IMT)- 2000 project. It evolves current GSM systems. Note: different from 3GPP2, which is another 3G technology based on IS-95 (CDMA), commonly known as CDMA2000.

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Standard Releases

Version Released Description at

Release 98 1998 This and earlier releases sppypecify pre-3G GSM networks

Release 99 2000 Q1 Specified the first UMTS 3G networks, incorporating a CDMA air interface

Release 4 2001 Q2 Added features including an all-IP Core Network

Release 5 2002 Q1 Introduced IMS and HSDPA Release 6 2004 Q4 Integrated operation with Wireless LAN networks Release 7 2007 Q4 Performance improvement

Release 8 Mar. 2009 LTE, All-IP Network (SAE). Release 9 Dec. 2009 SAES Enhancements, Wimax and LTE/UMTS Interoperability Release 10 In LTE Advanced progress 76 From wikipedia

38 LTE-advanced Proposals

Various concepts for Relay Nodes UE Dual TX antenna solutions for SU-MIMO and diversity MIMO Scalable system bandwidth exceeding 20 MHz, Potentially up to 100MHz Local area optimization of air interface Nomadic / Local Area network and mobility solutions Flexible Spectrum Usage Cognitive Radio Automatic and autonomous network configgpuration and operation Enhanced precoding and forward error correction Interference management and suppression Asymmetric bandwidth assignment for FDD Hybrid OFDMA and SC-FDMA in uplink UL/DL inter eNB coordinated MIMO From wikipedia 77

LTE vs WiMAX: Air interface

LTE WiMAX FDD and TDD TDD primary profile but Duplexing method but FDD focus FDD specifie d too MIMO mode Diversity/SM/CSM Diversity/SM/CSM System Bandwidth Scalable: 1.25 ~ 20 MHz Scalable: 3.5 ~ 10 (20) MHz Modulation 64QAM/16QAM/QPSK 64QAM/16QAM/QPSK FFT 128 ~ 2048 points 128 ~ 1024 (2048) points Downlink Access OFDMA OFDMA Uplink Access SC-FDMA OFDMA Frame Length 0.5ms 5 ms

Source: D. Pulley of Picochip

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39 Less obvious at first glance

Mobile WiMAX 20MHz is coming! LTE has two TDD modes with different frame structures: ƒ pressure is on to reduce on a single one “TDSCDMA successor mode” ƒ this may pre-empt natural selection and resultant could go head to head with WiMAX TDD profile SC-FDMA in the Uplink? ƒ WiMAX OFDMA has a peak-mean ratio of approx 10dB ƒ LTE SC-FDMA has lower peak-mean ratio: approx 5dB ∴ LTE terminal battery life should be better High speed packet data rate claims: ƒ regardless of air interface, divide the theory or marketing by 3 for deployable peak base station throughputs for wide area coverage

Source: D. Pulley of Picochip

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Over the next 5 years HSPA builds on existing 2G/3G deployments, licenses and roaming, and will account for majority of mobile wireless networks Mobile WiMAX can capture niche market dependent on spectrum availability, proof of performance (Sprint-Nextel) Initial coverage limited deployments give HSPA advantage in CAPEX and OPEX and therefore capital required for launch and NPV Lower cost of equipment will not be significant factor Important to consider other areas such as mobility, latency, services to be offered, revenue streams, and overall “ eco- system”

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40 Longer Term Perspective

Improvements in technology performance and resulting link budget (e.g. 802.16m) can give advantage to WiMAX particularly for Greenfield operators – but LTE will have advantage of 3GPP hiheritage Later capacity limited scenarios are more favourable to mobile WiMAX and LTE – mainly in urban areas – but greater competition from e.g. WiFi hotspots 3GPP and 3GPP2 networks migrate towards OFDMA technology (e.g. LTE, CDMA Rev. C) This may lead to further market consolidation, depending on speed of LTE/Rev. C and success of current mobil e WiMAX deployments

Who will eventually win? Who knows!

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Comparison WiMAX

Netw or k Large Simplicity Coverage WiFi Broad Band

Full Security QoS Mobility

3G /HSDPA

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41 Wireless Technology Positioning

Mobility / Range

High Speed

Vehicular Rural Flash‐OFDM Vehicle Vehicular GSM WiMAX with Urban GPRS UMTS limited mobility Pedestrian

alk HSDPA EDGE W Nomadic IEEE 802.16e Fixed urban Indoor DECT WLAN IEEE Fixed Personal Area Bluetooth (IEEE 802.11x) 802.16d Data rates Mbps 1 10 100 0.1 Capacity

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Agenda

Wireless LAN (Local Area Networks) Wireless MAN: WiMAX (IEEE 802.16) Mobile Cellular Systems 3GPP LTE (Long Term Evolution) Femto cell and Mobility Q&A

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42 Smartphones

Windows Mobile Based: 12% of the market, supports UMTS, WiFi. Symbian Based: 65% of the market, Nokia, Sony Ericsson, support 3G. RIM OS Based: 11% of the market, Blackberry (not currently 3G capable to save battery, with the small exception) Mac OS-like iPhone-OS Based: 7% of the market. Apple's iPhone (using EDGE)

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Femto Cell Also called Access Point Base Station No dual-mode handset needed, existing handset is fine. A femto cell is a small cellular base station, typically for indoors, especially where access would otherwise be limited or unavailable. The femtocell incorporates the functionality of a typical base station but extends it to allow a simpler, self contained deployment Although much attention is focussed on UMTS, the concept is applicable to other network technologies, such as GSM, CDMA2000, TD-SCDMA, WiMAX. Attractions to mobile oppperators: to improve both coverage and capacity, especially indoors. ƒ There may also be opportunity for new services and reduced cost.

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43 Femto Cell Network Arch.

Femto Cell BS

Macro Cell BS

Broadband Router Macro Network

Internet

Tunnel Mobile Operator Core Network

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Example Scenario

Nation Wide City WideWideCity NetworkNetwork NetworkNetwork (Cellular)(Cellular) (WiMAX)(WiMAX)

Home Office Network NetworkNetwork (Multiple WiFisWiFis)) (WiFi)(WiFi)

S w itc h Switch automatically and seamlessly from one network to another 88

44 Contact, Q&A

Dr Kun Yang School of Comp. Science & Electronic Engineering (CSEE), University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK Email: [email protected] http://privatewww.essex.ac.uk/~kunyang/

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