【文章內(nèi)容簡(jiǎn)介】 候選導(dǎo)頻集 46 軟切換 Threshold amp。 Timer TAdd TComp TDrop TTdrop Search, pare, bine, then Soft handoff 47 軟切換參數(shù) Pilot Strength TComp TAdd Tdrop TTdrop Time Active Pilot Neighbor or Remaining Neighbor Active Candidate 48 分集技術(shù)： ? 信號(hào)元素合并 (Rake 接收機(jī) ) ? 幀選擇 49 Rake接收機(jī) 50 Path Diversity Improves Voice Quality Receiver Receiver Receiver Mobile Rake Receiver Analog TDMA Calls Fading D/A Audio Fading D/A Mobile Receiver CDMA Calls Effects of fading are mitigated through use of multiple receivers that sum radio signals from different cells and from reflected rays. Fading is more likely to cause loss of information = lower speech quality 51 Soft Handoff Improves Voice Quality Multiple receive paths Switch Frame Quality Indicator Quality Frames Frame Quality Indicator Quality Frames Quality Frames Improved Speech Quality Transcoder picks best frame from up to three soft handoff cells. CDMA Soft Handoff Improves Frame Quality 4 3 2 1 4 3 2 1 seven frames shown in this example 1 2 3 4 5 6 7 1 1 2 2 3 3 4 4 5 5 6 6 7 7 Chosen frames of Transcoder 52 Frequency Diversity Improves Voice Quality Outgoing Waveform 80 dB 90 db 110 db 120 db Mhz Mhz This 400 Khz fade of 12 db only affects 1/3 of CDMA bandwidth. Therefore, total fade to CDMA user is 2 db The entire 30 KHz Channel of TDMA is affected by this same fade. Therefore, total fade to end user is 12 db. CDMA Offers More Protection Against Frequency Selective Fading Received Waveform 80 db 90 db 110 db 120 db 30 Khz Outgoing Waveform 80 db 90 db 110 db 120 db 30 Khz Received Waveform 80 db 90 db 110 db 120 db 12 dB Fade 2 dB Loss 12 dB Fade 12 dB Loss! CDMA TDMA 53 ? 碼分多址的基本原理 ? 碼分多址的關(guān)鍵技術(shù) ? CDMA同 GSM的比較 59 ? Cdma2022 1X 技術(shù)特點(diǎn) ? cdma2022 1X 網(wǎng)絡(luò)結(jié)構(gòu) 60 cdma20221X 技術(shù)特點(diǎn) 61 Performance Enhancements ? Reverse Link Pilot for Each Mobile ? True QPSK Modulation ? Continuous Reverse Link Waveform ? Improved Convolutional Encoding for kbps Voice Channels ? Fast Forward amp。 Reverse Link Power Control ? Supports Auxiliary Pilots for Beam Forming ? Forward Link Transmit Diversity OTD, MultiAntenna cdma 2022 62 Reuse of TIA/EIA95B ? cdma2022 is Fully Backwards Compatible with TIA/EIA95B ? Reused Aspects of TIA/EIA95B: ? TIA/EIA95B Radio Interface ? IS707 Data Services ? IS127 EVRC 8 kbps Vocoder and IS733 13 kbps Vocoder ? IS637 SMS amp。 IS683 Over the Air Activation ? IS98 and IS97 Minimum Performance Standards ? Common Broadcast Channels (Pilot, Sync Paging) ? Allows cdma2022 to be Deployed Sooner 63 cdma2022 Terms amp。 Definitions ? Chip ? A chip is a data bit at the final spreading rate ? SR Spreading Rate ? Defines the final spreading rate in terms of Mcps. So a Mcps system is called a SR3 system. ? RC Radio Configuration ? Defines the physical channel configuration based upon a base channel data rate. ? RCs contain rates derived from their base rate. For example, RC3 is based on kbps and includes , , , , , , , , and kbps. ? RCs are coupled to specific Spreading Rates 64 cdma2022 SR1 ? Is an Improved TIA/EIA95B Narrowband System ? Occupies the Same MHz Bandwidth as TIA/EIA95B – Forward Link: ? Adds Fast Power Control ? Uses QPSK Modulation Rather than Dual BPSK to: – Use 3/8 Rate Convolutional Encoder instead of 3/4 for Service (improves error correction) – 128 Walsh Codes to Handle More Soft Handoffs for service – Reverse Link: ? Uses Pilot Aided BPSK to Allow Coherent Demodulation ? Uses 1/4 Rate Convolutional Encode Instead of 1/2 or 1/3 ? Uses HPSK Spreading ? Enhance System Capacity 65 cdma2022 1X 要點(diǎn) ?技術(shù)改善 ? 對(duì)數(shù)據(jù)應(yīng)用支持 MAC, QoS, 和 turbo碼 ? 快速前后向功率控制 ? 反向信道相干解調(diào) ? 后向兼容 IS95A/B Operator Benefits ? 可支持高達(dá) bps數(shù)據(jù)速率 ? 與 IS95A/B相比，數(shù)據(jù)應(yīng)用能力有 46倍的提高 ? 與 IS95A/B相比， 話音容量有 ，減小了運(yùn)營(yíng)成本 ? 在保護(hù) IS95A/B投資的前提下，提供了經(jīng)濟(jì)有效的過渡策略 66 CDMA2022 1x 原理