【正文】 g is wasteful of valuable spectrum while packet switching is more efficient 對于數(shù)據(jù)應用來說 ,傳統(tǒng)的電路交換浪費了寶貴的頻率資源 ,而分組交換在數(shù)據(jù)應用方面對頻率利用的效率則高得多 ? GPRS is a way to provide wireless data service using the mature GSM technology and work. GPRS提供了在現(xiàn)有成熟的 GSM技術及網(wǎng)絡中實施數(shù)據(jù)服務的方案 ? GPRS subscribers will be permanently connected, just like PC in the office LAN GPRS終端可以長時間保持與網(wǎng)絡的連接 , 就象 PC機連接在辦公室內的局域網(wǎng)上一樣 GPRS Standard and SMG GPRS標準及 SMG ? GPRS standard is made by ETSI GPRS標準是由 ETSI制定的 ? ETSI stands for European Telemunication Standards Institute ETSI是歐洲通信標準協(xié)會的英文縮寫 ? ETSI can be visited at ETSI的主頁在 ? SMG stands for Special Mobile Group A subanization of ETSI SMG是 ETSI技術委員會的一個下屬機構 特別移動組 ? SMG hold two major meetings each year, finalize standard changes on the meeting, SMG31 stands for the standard version till the 31th SMG meeting SMG每年舉辦兩次大會 ,并在會議上通過對標準的修訂案 , 通常提到的 SMG31代表直到第 31屆 SMG大會為止的標準版本 ? GSM/GPRS technical specifications are divided into 13 parts GSM/GPRS技術規(guī)范都分為 13個部分 GSM/GPRS Technical Specification Category GSM/GPRS 技術規(guī)范分類 ? 00 Preamble 導言 01 General 總則 ? 02 Service Aspects 服務方面 03 Network Aspects 網(wǎng)絡方面 ? 04 MSBSS interface and Protocols 移動臺與基站系統(tǒng)的接口及協(xié)議 ? 05 Physical Layer in the Radio Path 無線通道的物理層 ? 06 Audio Aspects 無線方面 ? 07 Terminal Adaptors for Mobile Station 移動臺的終端適配器 ? 08 BTS/BSC and BSC/MSC Interface BTS/BSC和 BSC/MSC接口 ? 09 Network Interworking 交互網(wǎng)絡 ? 10 Service Interworking 交互服務 ? 11 Equipment Specification and Type Approval Specification 設備規(guī)范及批準類型規(guī)范 ? 12 Network management including Operations and Maintenance 網(wǎng)絡管理 ,操作及維護 GPRS Technical Specification Example GPRS 技術規(guī)范范例 ? Requirements Specification of GPRS GPRS需求規(guī)范 ? Service description Stage 1 服務描述 (第一階段 ) ? Service description Stage 2 服務描述 (第二階段 ) ? RLC/MAC protocol 無線鏈路控制及媒體訪問控制協(xié)議 ? LLC Specification 邏輯鏈路控制協(xié)議規(guī)范 ? Subwork Depend Convergence Protocol 子網(wǎng)依賴集中協(xié)議 ? Mobile Station supporting GPRS 支持 GPRS的移動臺 ? BSSSGSN interface。 14 dB (near 75% BLER improvement) CS4對載干比在 614分貝間的變化反應明顯 (塊錯誤率降低 75%) Typical Urban 3 km/h No Hopping 典型城區(qū) ,移動速度每小時 3公里 ,無跳頻 Throughput TU3 No Hopping 信道數(shù)據(jù)流速 TU3 無跳頻 0 5 10 15 20 25 0 4 8 12 16 20 24 C/I載干比 (dB) CS1 CS2 CS3 CS4 ? CS1 amp。 CS4 inefficient at low C/I CS3和 CS4在低載干比時效率很低 ? All Schemes converge to Max rate at high C/I 隨載干比的增高各編碼方案均收斂于其最高速率 ? CS3 amp。 BSSGP GPRS基站系統(tǒng)協(xié)議 ? SGSNVLR。 Data in Hopping Networks 跳頻網(wǎng)絡中的話音與數(shù)據(jù) ? GPRS RF coverage GPRS的無線覆蓋特性 ? Wireless Data Traffic Model 無線數(shù)據(jù)流量模型 ? QoS in GPRS GPRS的服務質量 GSM Speech Air Interface Coding (1) GSM話音空中接口編碼 (1) ? Each 20ms of GSM, speech uses 456 bits across air interface GSM中每 20毫秒為一時系 ,話音的空中接口編碼為 456比特 – Convolutional coding applied for Forward Error Correction 卷積編碼用于前向除錯 – 45% of bits are for error correction 45%的比特用于除錯 – 2 levels of interleaving to minimise effect of Rayleigh fading 兩級交織使瑞利衰退影響為最小 – Convolutional codes allow recovery of lost bits 卷積可以恢復丟失的比特 – Perception of listener can also fill gaps 受話者的直覺可以容忍些微話音的丟失 – High BER/FER = Poor speech quality and NO retransmissions 高錯誤率將導致話音質量變差 ,不會有重傳發(fā)生 Class 1a 50 bits 260 bits 50 bits 3 bits 132 bits 4 bits 378 bits 78 bits Tail bits Parity Convolutional Code 456 bits 57 bits Even 57 bits Odd 57 bits Even 57 bits Odd 57 bits Even 57 bits Odd 57 bits Even 57 bits Odd Diagonal Interleaving 8 consecutive TDMA burst over the Um air interface Class 1b 132 bits Class 2 78 bits GSM Speech Air Interface Coding (2) GSM話音空中接口編碼 (2) Um Ne t w o r kS NDCPLLC( Not e)RLCM A CP hy s . L i nkP hy s . RFS NDCPLLCRLCM A CP hy s . L i nkP hy s . RFMSS co p e o f G S M 0 3 . 6 0S co p e o f G S M 0 3 . 6 4No t e : I n t h e n e t w o r k t h e L L C issp li t b e t w e e n B S S a n d S G S N.T h e B S S f u n ct io n a li t y is ca ll e dL L C r e la y .GPRS Data Air Interface Coding GPRS數(shù)據(jù)空中接口編碼 ? Data must be decoded in perfect condition, unlike speech 不象話音 ,數(shù)據(jù)在解碼中不允許任何錯誤 ? If errors cannot be corrected, retransmission is required 如果錯誤無法糾正 ,則必須重傳 ? RLC layer controls backward error correction over Air Interface RLC層控制空中接口的后向除錯 C o d i n g S c h e m eC o d e d b i t sP u n c t u r e db i t sD a t aR a t e( k b p s )M u l t i p l e S l o tM a x .D a t aR a t e( k b p s )C S 1 456 0 9 . 0 5 7 2 . 4C S 2 588 132 1 3 . 4 1 0 7 . 2C S 3 676 220 1 5 . 6 1 2 4 . 8C S 4 456 0 2 1 . 4 1 7 1 . 2M a x . P e r T S D a t a r a t e ( k b p s )0510152025C S1 C S2 C S3 C S4KBits per SecondGPRS Coding Schemes GPRS的編碼方案 ? GPRS using same physical RF layer as GSM speech GPRS 用與 GSM 話音同樣的物理層 ? Data is coded into normal bursts 數(shù)據(jù)也在普通脈沖 內編碼 (456 bits / 20ms) ? Higher data rates per timeslot achieved by removing error protection 每時系的更高數(shù)據(jù) 傳輸速度是以降低 容錯性能換來的 ? GPRS has four RF coding scheme GPRS有四種無線編碼方式 ? The throughput rate in table below is for physical layer on air interface 下表中最后一列的數(shù)據(jù) , 是指空中接口物理層的最高速度 ? 右表中的最后一列數(shù)據(jù) 是指邏輯鏈路控制層的 最高數(shù)據(jù)流量 ,當 RLC 層中有可選項時速率還 會低一些 S c he m e C od eR a t eU S Fbi t sP r e c od e dU S Fbi t sR a di oB l oc k( e x c l . U S Fa nd B C S )BCS Ta i lbi t sC od e dbi t sP un c t ur e dbi t sD a t aR a t e( k bp s )C S 1 1 / 2 3 3 181 40 4 456 0 9 . 0 5C S 2 ~ 2 / 3 3 6 268 16 4 588 132 1 3 . 4C S 3 ~ 3 / 4 3 6 312 16 4 676 220 1 5 . 6C S 4 1 3 12 428 16 0 456 0 2 1 . 4S c he m e M A CH e a de r( e x . U S F)( bi t s )S pa r ebi t sR LCD a t a( oc t e c t s )R LCU s e rD a t a( oc t e c t s )U s e rD a t a