3GPP Wireless Standard

Transcription

1 3GPP Wireless Standard Shishir Pandey School of Technology and Computer Science TIFR, Mumbai April 10, 2009 Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

2 3GPP Overview 3GPP : 3rd Generation Partnership Project It is a collaboration between groups of telecommunications associations, to make a globally applicable third generation (3G) mobile phone system 3GPP should not be confused with 3GPP2 3GPP Specifications are also refered to as UTRAN, UMTS(in Europe) and FOMA(in Japan) The first release of the specification was in the year 1998 (Release 98) Release 98 - Specifies pre-3g GSM Networks Release 99 - Specified the first UMTS 3G Networks, incorporating a CDMA interface Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

3 3GPP has the following technologies GSM : Global System for Mobile GSM include GPRS (General Packet Radio Service) and EDGE (Enhanced Data rates for Global Evolution) WCDMA - Wideband Code Division Multiple Access HSPA - High Speed Packet Access LTE - Long Term Evolution Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

4 GSM GSM is Circuit Switched Network Ideal for delivery of voice but limitations for sending data Data, internet traffic is bursty and hence, circuit Switched network is highly inefficient resource utilization. For Bursty traffic packet switched network is better. GPRS (in 2000) added packet switched functionality EDGE: 3 fold increase in bit rate (8PSK replacing GMSK) GPRS and EDGE are largely specified in the GSM EDGE Radio Access Network (GERAN) group of 3GPP Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

5 Challenges faced by GSM Demand for data from networks like the internet For a circuit switched network total connection time is the billed time. Requirement of different billing system for data - based on amount of data transferred Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

6 GPRS GPRS added packet switched functionality to GSM Offers more user friendly billing- Billing is based on the amount of transmitted data. GPRS speed: Theoretically 171Kbps (Downlink), 14Kbps (Uplink) by using more than one timeslot of the TDMA frame Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

7 GPRS Physical Layer Fig: GSM carrier frequencies, duplexing, and TDMA frames. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

8 GPRS Physical Layer contd.. Two frequency bands 45MHz apart have been reserved for GSM operation MHz for uplink MHz for downlink Each band of 25MHz is divided into 124 single carrier channels of 200KHz width. Each of the 200KHz channels carries 8 TDMA channels Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

9 GPRS Physical Layer contd.. The recurrence of one particular time slot defines a physical channel. A GSM MS uses the same time slot in the uplink and the downlink GPRS allows a single MS to transmit on multiple time slots of the same TDMA. In good channel conditions transmission without Convolutional coding and can achieve data rates of 21.4Kbps per time slot. With eight time slots Max speed can be Kbps. In practice multiple users share time slots and hence 40kbps per user will be achieved. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

10 GPRS Session Management Fig: PDP Context activation Apply for addresses (eg. IP address) used in PDN (Packet Data Network) Once it gets the address it can get data packets. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

11 EDGE FIG: GSM/GPRS Network Architechture The core of GPRS network is independent of user bit rate. No new hardware required In the radio network base station transceivers need to be EDGE capable and base Station software needs to be updated. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

12 EDGE continued.. EDGE employs a new moduldation scheme - 8PSK (replacing GMSK). Nine Modulation and coding schemes are defined in EDGE. Link quality control dynamically selects the modulation and coding scheme. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

13 EDGE Evolution Latency reduction - By reducing TTI (Transmission Time Interval) from 20ms to 10ms Higher order modulation - Using 16 QAM instead of 8PSK Using turbo codes instead of convolution codes. 12 modulation schemes (16QAM and 32QAM used) peak bit rate is 100kbps per timeslot Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

14 WCDMA WCDMA is a spread spectrum modulation technique Information speard over approx. 5MHz 10ms radio frame is divided into 15 slots 2560 chips/slot, 3.84Mbps is the chip rate PHY channel defined as codes and additionally in TDD mode the sequence of time slots Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

15 WCDMA GSM BSS and WCDMA RAN are connected to the core GSM network. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

16 Radio Network Functionality Power Control: For each subscriber the base station must receive the same power level from all handsets regardless of the distance WCDMA updates power levels 1500 times every second Power control - gives rise to Cell Breathing -trade-off between coverage and capacity. Channel Type Switching: Two Basic Channels are - Common and Dedicated This type of functionality is used to switch subscribers between channels Dedicated Channel used when lot of inforamtion to be transmitted eg. Voice Common Channel reduces delays as many users can share the same resource. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

17 WCDMA Frame Structure FIG: WCDMA Radio Frame Structure Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

18 WCDMA Physical Layer Contd.. Each slot in a radio frame carries a set of common channels and dedicated channels. Information rate of channel 7500 symbols/sec to symbols/sec in the downlink symbols/sec to symbols/sec in the uplink The difference is due to the difference in the spreading factors. Spreading Factor: From 256 to 4 with FDD uplink From 512 to 4 with FDD downlink Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

19 HSDPA Key features of HSDPA are: Higher order modulation - Also uses 16QAM along with QPSK to provide Higher data rates. Short Transmission Time Interval(TTI) - from 10ms to 2ms Downlink Speeds upto - 14Mbps Fast Link Adaptation Fast scheduling Fast Hybrid Automatic Repeat request(arq) Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

20 HSDPA: Fast Link Adaptation WCDMA used Power control to compensate for differences and variations in radio channel conditions. So available o/p power was not fully used as power needed to be reserved for ongoing connections. Surplus of o/p power cannot be used to increase the throughput of the system. HSDPA - Relies on bit-rate adjustment (known as Link Adaptation) Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

21 Scheduling Fig: Schedule users with favorable radio conditions Fast Scheduling: determines the user equipment (UE) the shared channel transmission should be directed to. (users with favourable radio conditions) Terminals using High Speed services send regular channel quality reports Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

22 Thankyou Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23

23 Circuit Switched Network Circuit Swithcing n/w is one that establishes a circuit or channel (by allocating resouces - Frequency intervals in FDM and time slots in TDM) between node before the users may communicate. Shishir Pandey (TIFR) 3GPP Wireless Standard April 10, / 23