Cellular Industry Landscape Suresh Kalyanasundaram Global Telecom Solutions Sector Motorola Arlington Heights Illinois, USA

Outline Cellular industry overview Role of standards Generations of cellular technologies Sketchy details of GSM air interface Enhancements to GSM air interface for GPRS/EDGE Wireless link and interactions with TCP Where to next? (3G vision, WLANs, etc.)

How the industry is organized? Chip manufacturers Texas Instruments, Qualcomm, Motorola, etc. Equipment manufacturers Motorola, Nokia, Ericsson, Siemens, Lucent, etc. Operators In India: Hutch, Bharti Cellular, Reliance, Airtel, etc. In US: Cingular, AT&T, Nextel, Vodafone

Equipment manufacturers Handset manufacturers Motorola, Nokia, etc. LG, Samsung, SonyEricsson etc. Infrastructure equipment manufacturers Motorola, Nokia, etc. Lucent, Nortel, etc.

Typical Voice Network Architecture (GSM, 2G) PSTN MS- Mobile Station BTS - Base transceiver station BSC - Basestation controller MSC - Mobile switching center PSTN - Public switched telephone network MSC BSC BTS BTS MS MS MS

Interfaces Standardized open interfaces between different network elements Example: BTS to MS interface is called the air interface BTS from one manufacturer should be able to operate with MS from another manufacturer Standards bodies define messages exchanged across open interfaces Encourages competition

Role of standards bodies Define network architecture Apportion tasks to different network elements Define open interfaces and messages exchanged across those interfaces Define protocols across open interfaces Set expected performance standards from different network elements Example: ETSI (European Telecommunications Standardization Institute) defined the GSM (Global system for mobile communications) standards

Families of Standards Currently two main families of standards: GSM and CDMA GSM — GPRS — EDGE — UMTS — HSDPA IS-95 — CDMA 1X — CDMA 1X EV-DO/DV 3GPP (Third generation partnership project): Handles GSM family of standards 3GPP2: Handles CDMA family of standards

How manufacturers distinguish their products Is everything standardized? If everything is standardized, how do manufacturers distinguish their products? No, not everything is standardized. Manufacturers have a lot of freedom to decide what proprietary algorithms go in the different network elements within the constraints imposed by the standards

Generations of cellular technologies 1G: Analog cellular voice Examples: AMPS (American mobile phone system), NMT (Nordic mobile telephony) 2G: Digital cellular voice Examples: GSM, IS-95, PDC, US-TDMA (IS-136) Provided significant capacity increase and voice quality improvement over 1G

Generations of cellular technologies (Cont’d) 2.5G: Digital cellular voice + low-speed packet switched data Examples: GPRS (General packet radio service), EDGE (Enhanced data rates for GSM evolution), CDMA 1X 3G: Fully integrated voice + high-speed packet data (upto 2 Mbps) Examples: UMTS (Universal mobile telecommunications system), CDMA 1X EV-DO/DV

Cellular Packet Data (2.5G/3G) Enables wireless web browsing, access to e-mail, FTP, etc. Provides the same ubiquitous coverage provided by cellular voice. Packet-switching technology over the air interface Enables charging only for times when the user has data to transmit Efficient use of air interface resources to suit bursty data traffic

Some details of GSM air interface The spectrum allocated to GSM is divided into 200 KHz carriers. (FDMA, Frequency division multiple access) Each carrier is divided into frames with 8 timeslots (TDMA, Time division multiple access) Hybrid FDMA/TDMA multiple access scheme

Enhancements to GSM air interface for GPRS/EDGE Adaptive modulation and coding (AMC): For voice, a single modulation and coding scheme (MCS) is chosen to give reasonable performance for users at the cell edge. Other users closer to the cell center have better channel conditions, but cannot exploit it. With AMC, users with better channel conditions reduce the coding to get more useful bits across.

Adaptive Modulation and Coding (Cont’d) Multiple modulation and coding schemes to make use of better radio conditions CS 1-4, provides rates of 8-20 kbps per timeslot in GPRS MCS 1-9 provides rates of 8-59.2 kbps per timeslot in EDGE Dynamic MCS selection

Enhancements to GSM air interface (Cont’d) Timeslot allocation Each user can be allocated multiple timeslots (for voice, a user is allocated only a single timeslot) Multiple users can be allocated the same timeslot Each user can be allocated a maximum of 8 timeslots (according to standards, but there are no handsets available yet).

Enhancements to GSM air interface (Cont’d) Assuming good channel conditions => CS-4 usage, a user can get upto 160 kbps in GPRS Assuming MCS 9 a user can get upto 473.6 kbps in EDGE Allowing multiple users to share a timeslot enables usage of air interface resources by other users when a certain user is idle

Enhancements to GSM air interface (Cont’d) “Always on” connection -- Similar to PCs connected to LANs Unlike “dial-up” connections that require elaborate procedure to get a session going Allows operators to charge only for the traffic that a user generates

New Network Elements for GPRS/EDGE PSTN Internet GGSN SGSN MSC PCU BSC Combined voice and data path BTS Data path BTS Voice path MS MS MS

New Network Elements (Cont’d) PCU – Packet control unit SGSN – Serving GPRS support node GGSN – Gateway GPRS support node

Wireless Link and TCP Transmission Control Protocol (TCP) runs end-to-end between the mobile terminal and the server Errors on wireless links much higher than that on wired links TCP is designed for wired networks, and TCP running at the sender reduces transmission rate when it sees errors occurring on wireless links TCP interprets packet losses as indication of congestion

Wireless Link and TCP (Cont’d) However, these errors are due to error-prone wireless medium Radio link control (RLC) protocol tries to hide the wireless link from TCP RLC performs hybrid ARQ (automatic repeat request) protocol Hybrid of forward error correction (FEC) and local retransmissions

Simplified protocol stack Application Application TCP TCP IP IP RLC RLC MAC MAC GSM RF PCU Server MS

The 3G vision (UMTS) A user can get upto 2 Mbps, under good channel conditions, if they get exclusive access to a carrier Even under poor channel conditions, users can get 384 kbps, if they get exclusive access to a carrier Based on WCDMA (wideband code division multiple access) technology 5 MHz carriers instead of 200 KHz narrowband carriers

The 3G vision (Cont’d) Support for multimedia Capability to meet the different Quality of Service (QoS) requirements of different traffic types Four different traffic classes identified Conversational (conversational voice, video telephony, etc.) Streaming (Streaming audio and video) Interactive (Interactive web browsing, telnet, etc.) Background (Background download of emails, FTP, etc.)

Challenges today’s cellular industry Over capacity and falling prices Heavy recruitment in anticipation of unrealistic future growth expectations Huge license fees to obtain 3G licenses Requirement to entirely replace existing equipment to move to UMTS from GSM/GPRS/EDGE. Competition from WLANs (Wireless local area networks)

Wireless Local Area Networks Smaller coverage area, but higher bitrates (up to 10 Mbps) Cheap access points and WLAN cards Unlicensed spectrum Ubiquity may not be needed for data People drive a lot in the west, but will not be browsing the Internet while driving. Only need wireless data at airports, highway rest areas, coffee shops, etc. In Japan, wireless data has become more popular because Japanese use trains

Conclusions Huge scope for cell phone penetration in developing nations, such as, India. Low telephone density Can be used as an alternative to non-existent landline connections In developed nations, very high penetration rates already Need wireless data to take off Wireless data will become popular eventually Question is if it will be the WLAN variety or the cellular variety