Iterative data detection and channel estimation for advanced TDMA systems

This letter presents a new receiver for Q-ary transmission, where all receiver blocks are embedded in an iterative structure. Packet data transmission in Global Systems for Mobile communications (GSM) and Enhanced Data rates for Global Evolution (EDGE) are considered as examples. A low-complexity soft-in-soft-out detector for EDGE is introduced and its modification suitable for iterative detection is derived. Application of iterative detection and channel estimation techniques in GSM/EDGE shows a significant performance enhancement. Additional improvement may be obtained if the iterative processing is applied to packet retransmission schemes.     

基于DSP的双路信道无线视频终端设计

以高性能DSP为设计核心,采用H.264编码,利用双路增强型数据业务(EDGE)信道,将视频流发送到视频服务器.提出了基于双路缓冲区判断的发送控制策略,详细描述了系统结构及软硬件设计.实验结果表明,CIF格式的图像传输基本能达到实时的要求.     

增强型数据业务EDGE技术

增强型数据业务(EDGE)是将现有第二代TDMA移动通信系统推向第三代移动通信系统平滑过渡的一种方案，主要在第二代GSM中采用了一种改进的多电平8—PSK调制方式。因此介绍了EDGE的概念、发展过程、技术标准、承载业务等，并分析了在现有GSM网中部署EDGE对原有网络系统产生的影响。     

Joint equalization and interference suppression for high data ratewireless systems

Enhanced Data Rates for Global Evolution (EDGE) is currently being standardized as an evolution of GSM in Europe and of IS-136 in the United States as an air interface for high speed data services for third generation mobile systems. In this paper, we study space-time processing for EDGE to provide interference suppression. We consider the use of two receive antennas and propose a joint equalization and diversity receiver. This receiver uses feedforward filters on each diversity branch to perform minimum mean-square error cochannel interference suppression, while leaving the intersymbol interference to be mitigated by the subsequent equalizer. The equalizer is a delayed decision feedback sequence estimator, consisting of a reduced-state Viterbi processor and a feedback filter. The equalizer provides soft output to the channel decoder after deinterleaving. We describe a novel weight generation algorithm and present simulation results on the link performance of EDGE with interference suppression. These results show a significant improvement in the signal-to-interference ratio (SIR) performance due to both diversity (against fading) and interference suppression. At a 10% block error rate, the proposed receiver provides a 20 dB improvement in SIR for both the typical urban and hilly terrain profiles     

EGPRS无线网络规划

随着GSM用户对无线数据业务提出更高要求,基于GSM网络的增强数据率解决方案逐渐被运营商引入,作为移动通信平滑演进的过渡解决方案.本文介绍了EGPRS的技术特点、着重分析了EGPRS网络规划的主要特点,并和传统GSM网络规划方法进行比较分析.     

EGPRS和cdma 1x无线数据业务性能对比研究

EGPRS是一种基于GSM/GPRS网络的数据增强型通用分组无线业务,它充分利用了现有的GSM/GPRS网络资源,保护运营商的投资,在第三代移动网络商业化之前提前为用户提供个人多媒体通信业务。cdma1x是基于CDMAIS95网络的升级,是通往cdma2000的过渡阶段,同样也提供较大容量的数据业务支持。本文主要针对EGPRS和cdma1x技术的无线性能和特点在理论上进行了对比分析,之后通过对某城市的两种网络进行了实地测试,重点从用户体验的角度考察和对比了两种网络提供数据业务的能力。     

EDGE Phase 2核心技术：GERAN

本文介绍了ＥＤＧＥ（Ｅｎｈａｎｃｅｄ Ｄａｔａ ｒａｔｅ ｆｏｒ ＧＳＭ Ｅｖｏｌｕｔｉｏｎ）在第二阶段的无线接入网ＧＥＲＡＮ（ＧＳＭ／ＥＤＧＥ Ｒａｄｉｏ Ａｃｃｅｓｓ Ｎｅｔｗｏｒｋ）的技术标准、业务功能等，并总结出与目前ＧＳＭ网络结构兼容的ＥＤＧＥ Ｐｈａｓｅ ２网络结构布局。     

Equalization concepts for EDGE

An equalization concept for the novel radio access scheme Enhanced Data rates for GSM Evolution (EDGE) is proposed by which high performance can be obtained at moderate computational complexity. Because high-level modulation is employed in EDGE, optimum equalization as usually performed in Global System for Mobile Communications (GSM) receivers is too complex and suboptimum schemes have to be considered. It is shown that delayed decision-feedback sequence estimation (DDFSE) and reduced-state sequence estimation (RSSE) are promising candidates. For various channel profiles, approximations for the bit error rate of these suboptimum equalization techniques are given and compared with simulation results for DDFSE. It turns out that a discrete-time prefilter creating a minimum-phase overall impulse response is indispensable for a favorable tradeoff between performance and complexity. Additionally, the influence of channel estimation and of the receiver input filter is investigated and the reasons for performance degradation compared to the additive white Gaussian noise channel are indicated. Finally, the overall system performance attainable with the proposed equalization concept is determined for transmission with channel coding     

Improved spatial-temporal equalization for EDGE: a fastselective-direction MMSE timing recovery algorithm and two-stagesoft-output equalizer

The radio interface EDGE (Enhanced Data rates for Global Evolution) is currently being standardized as an evolutionary path from GSM and TDMA-IS136 for third-generation high-speed data wireless systems. For the EDGE system with multiple antennas, spatial-temporal equalization (STE) can reduce intersymbol interference and co-channel interference, thereby increasing the capacity and range. In this paper, we propose two new techniques to improve the performance of a previously proposed STE: a fast timing recovery algorithm for a selective time-reversal equalizer and a two-stage soft-output equalizer. The new timing recovery algorithm determines the estimated burst timing and processing direction by computing the minimum mean-square error (MMSE) for decision feedback equalizers in both the forward and reverse time directions. The two-stage soft-output equalizer is the cascade of a delayed decision-feedback sequence estimator (DDFSE) and maximum a posteriori probability (MAP) estimator. The DDFSE provides better noise variance estimation and channel truncation for the following MAP. The performance of the new STE is evaluated for the EDGE. At 10% block error rate, the two-branch receiver requires a 3-7-dB lower signal-to-interference ratio (SIR) than the previous approach. Compared with the one-branch receiver, the two-branch receiver requires a 4-dB lower SNR with noise only, and a 10-27-dB lower SIR with a single interferer     

Transmission algorithm for video streaming over cellular networks

2.5G and 3G cellular networks are becoming more widespread and the need for value added services increases rapidly. One of the key services that operators seek to provide is streaming of rich multimedia content. However, network characteristics make the use of streaming applications very difficult with an unacceptable quality of service (QoS). The 3GPP standardization body has standardized streaming services that will benefit operators and users. There is a need for a mechanism that will enable a good quality multimedia streaming that uses the 3GPP standard. This paper describes an adaptive streaming algorithm that uses the 3GPP standard. It improves significantly the QoS in varying network conditions while monitoring its performance using queueing methodologies. The algorithm utilizes the available buffers on the route of the streaming data in a unique way that guarantees high QoS. The system is analytically modeled: the streaming server, the cellular network and the cellular client are modeled as cascaded buffers and the data is sequentially streamed between them. The proposed Adaptive streaming algorithm (ASA) controls these buffers’ occupancy levels by controlling the transmission and the encoding rates of the streaming server to achieve high QoS for the streaming. It overcomes the inherent fluctuations of the network bandwidth. The algorithm was tested on General Packet Radio Service (GPRS), Enhanced Data rates for GSM Evolution (EDGE) and Universal Mobile Telecommunication System (UMTS) networks. The results showed substantial improvements over other standard streaming methods used today.     

无线载波分层接入技术在EGPRS优化中的应用

EGPRS对无线信道的物理特征较为敏感,通过无线载波分层接入技术为EGPRs业务指定业务信道,提高了EGPRS业务的传输速率,大幅提高了用户感知,同时由于该技术为不同业务提供差异化服务,为不同种类的业务优化也具有指导意义。     

Performance of data services in GERAN networks

The performance of data based services such as Internet browsing and e-mailing in GSM EDGE Radio Access Networks (GERAN) is described. Results from networks around the world show that quite significant performance differences exist, despite the fact that all systems are based on the same technical standard     

Statistical Estimation of Fast Varying Channels for Cellular Mobile Telecommunications Systems

The time variant environment in fast channels severely impacts on the performances of classical equalization techniques. A method is proposed here to circumvent this problem, particularly in the severe channel with fast behaviour. To improve the Bit Error Rate (BER) at the receiver, a new approach is proposed for the channel impulse response (CIR) estimation in the Enhanced Data rates for GSM Evolution (EDGE)cellular system. The computation of the CIR h(t) (finite impulse response filter) is performed by using the Least Squares algorithm. Then, a statistical estimation of the CIR is achieved to update the coefficients of the equalizer filter. Computer simulation results show that statistical estimation (CIR re-estimation) provides significant improvement with 250 km/h vehiclespeed (RA250): the bit error rate (BER) is 20% lowered for data bits far from the middle of the burst.     

Quad-band GSM/GPRS/EDGE polar loop transmitter

An enhanced data-rates for GSM evolution (EDGE) transmitter using a nonlinear GSM-type PA is presented. It is based on a novel polar loop architecture that employs separate feedback control of the amplitude and the phase of the output signal. With this approach, the problems with AM-to-PM as well as AM-to-AM of the nonlinear PA are essentially eliminated. In addition, this architecture allows for a large dynamic output power control range, as required by the GSM specification. The transmitter uses a standard I/Q interface and does not require the extraction of amplitude and phase modulation in the digital domain. The dual feedback loop ensures robust performance even under voltage-standing wave ratio variations without using an isolator. No external PA filtering is required to meet the transmitter noise in the receive band. The EDGE spectral mask is met with an rms error vector magnitude of <3% at 29 dBm at the antenna, corresponding to 2 dB above nominal maximum output power. There is no mode change between GMSK and EDGE, and the transmitter operates seamlessly in multislot Enhanced General Packet Radio Service. The polar modulation transmitter meets or exceeds the GSM-type approval requirements for both EDGE and GMSK in quad band (850/900/1800/1900 MHz).     

TBF分配算法优化

EDGE业务的快速发展,导致2G网络综合利用率高位运行。通过对现网数据的分析,发现可以通过提高PDCH复用度以大幅节省载频资源。针对因大量低速率业务占用引起的PDCH信道承载速率低的问题,提出了一种新的TBF资源分配方法。通过此方法的应用,可缓解低速率业务带来的网络压力,提升PDCH承载速率,提高网络承载效率。     

EDGE中的8PSK技术

改进数据率GSM服务(EDGE)是第二代GSM移动通信系统向第三代移动通信系统平滑过渡的新的无线接入技术。与GSM系统不同的是,EDGE在调制方式上没有采用高斯最小移频键控(GMSK)技术,而是应用了改进的八进制相移键控(8PSK)技术来提供更高的数据传输速率。文章介绍了EDGE技术的提出、基本概念及其采用的调制技术,阐述了8PSK技术的基本原理。     

Performance analysis and design of STBCs for frequency-selective fading channels

In this paper, space-time block-coded transmission over frequency-selective fading channels is investigated. A lower bound for the pairwise error probability for optimum detection is given. Also, an approximation for the bit-error rate is derived and compared with simulation results for maximum-likelihood sequence estimation (MLSE) for the GSM/EDGE (Enhanced Data Rates for GSM Evolution) system. Furthermore, a novel design rule for space-time block codes (STBCs) for frequency-selective fading channels is provided. A corresponding code is designed and shown to yield higher performance than Alamouti's code. It is demonstrated that for fading channels with L independent impulse response coefficients, STBCs designed for the flat fading channel can achieve at most a diversity order of (N/sub T/+L-1)N/sub R/ if N/sub T/ transmit antennas and N/sub R/ receive antennas are used. On the other hand, the maximum diversity order employing the proposed code design rule is LN/sub T/N/sub R/.     

基于GSM900M升级的EDGE＋＋应用及评估

EDGE＋＋的本质是FDD-LTE技术,可以通过升级农村的GSM900M且在共用现网TD-LTE的核心网、PTN传输网基础上改造完成。硬件上,将GSM900M的RRU替换为EDGE＋＋的RRU,BBU侧增加EDGE＋＋的基带处理板和主控板,GSM900M的天馈资源无需替换。软件上,通过Refarming GSM工具清理出农村的空闲频率5M,升级EDGE＋＋的eNodeB的软件版本,修改GSM900M的BTS的相关模式,联调EDGE＋＋的eNodeB,打通EDGE＋＋的eNodeB到EPC之间的PTN传输通道,完成eNodeB站点业务调测。最后,将EDGE＋＋信号通过支持EDGE＋＋的MiFi或CPE终端转换成Wi-Fi信号,在农村提供Wi-Fi热点。     

中国移动EGPRS数据业务的发展策略研究

中国移动EGPRS数据业务的快速发展,导致了2G网络综合利用率高位运行。通过对现网数据的分析和演绎提出在基本满足现有数据业务的条件下,近期可通过提高PDCH复用度以大幅节省数据载频资源,缓解数据业务压力;为了确保无线数据业务持续平稳发展,中远期的发展策略应重点关注EGPRS资源管控能力的提升和数据业务的有效分流。     

TCP/IP在GPRS/EGPRS网络中的应用及影响

通用分组无线业务/增强型数据速率演进技术（GPRS/EGPRS）服务扩展了当前世界上最流行的第二代移动系统——基于语音的GSM,使其能够收发基于分组的数据。随着移动通信技术的发展和业务的多样化,人们对数据业务的需求不断增加,GPRS/EGPRS网络优化也成为了重中之重。除传统的无线网络及核心网络优化外,将其以端到端的思路分析,看为无线＋IP网络技术,成为了新的优化思路。因此传输控制协议/因特网互联协议（TCP/IP）作为互联网固有的最为广泛的传输协议在无线分组数据业务网络中同样得到广泛应用。主要就TCP/IP协议在GPRS/EGPRS中的应用其影响进行了分析。