CDMA/HDR: a bandwidth efficient high speed wireless data servicefor nomadic users

This article presents an approach to providing very high-data-rate downstream Internet access by nomadic users within the current CDMA physical layer architecture. A means for considerably increasing the throughput by optimizing packet data protocols and by other network and coding techniques are presented and supported by simulations and laboratory measurements. The network architecture, based on Internet protocols adapted to the mobile environment, is described, followed by a discussion of economic considerations in comparison to cable and DSL services     

Sensor networks with mobile access: optimal random access and coding

We consider random access and coding schemes for sensor networks with mobile access (SENMA). Using an orthogonal code-division multiple access (CDMA) as the physical layer, an opportunistic ALOHA (O-ALOHA) protocol that utilizes channel state information is proposed. Under the packet capture model and using the asymptotic throughput as the performance metric, we show that O-ALOHA approaches the throughput equal to the spreading gain with an arbitrarily small power at each sensor. This result implies that O-ALOHA is close to the optimal centralized scheduling scheme for the orthogonal CDMA networks. When side information such as location is available, the transmission control is modified to incorporate either the distribution or the actual realization of the side information. Convergence of the throughput with respect to the size of the network is analyzed. For networks allowing sensor collaborations, we combine coding with random access by proposing two coded random access schemes: spreading code dependent and independent transmissions. In the low rate regime, the spreading code independent transmission has a larger random coding exponent (therefore, faster decay of error probability) than that of the spreading code dependent transmission. On the other hand, the spreading code dependent transmission gives higher achievable rate.     

Applying CDMA Technique to Network-on-Chip

The issues of applying the code-division multiple access (CDMA) technique to an on-chip packet switched communication network are discussed in this paper. A packet switched network-on-chip (NoC) that applies the CDMA technique is realized in register-transfer level (RTL) using VHDL. The realized CDMA NoC supports the globally-asynchronous locally-synchronous (GALS) communication scheme by applying both synchronous and asynchronous designs. In a packet switched NoC, which applies a point-to-point connection scheme, e.g., a ring topology NoC, data transfer latency varies largely if the packets are transferred to different destinations or to the same destination through different routes in the network. The CDMA NoC can eliminate the data transfer latency variations by sharing the data communication media among multiple users concurrently. A six-node GALS CDMA on-chip network is modeled and simulated. The characteristics of the CDMA NoC are examined by comparing them with the characteristics of an on-chip bidirectional ring topology network. The simulation results reveal that the data transfer latency in the CDMA NoC is a constant value for a certain length of packet and is equivalent to the best case data transfer latency in the bidirectional ring network when data path width is set to 32 bits.     

A multicarrier CDMA architecture based on orthogonal complementarycodes for new generations of wideband wireless communications

This article is a review of our ongoing research effort to construct a new multicarrier CDMA architecture based on orthogonal complete complementary codes, characterized by its innovative spreading modulation scheme, uplink and downlink signaling design, and digital receiver implementation for multipath signal detection. There are several advantages of the proposed CDMA architecture compared to conventional CDMA systems pertinent to current 2G and 3G standards. First of all, it can achieve a spreading efficiency (SE) very close to one (the SE is defined as the amount of information bit(s) conveyed by each chip); whereas SEs of conventional CDMA systems equal 1/N, where N denotes the length of spreading codes. Second, it offers MAI-free operation in both upand downlink transmissions in an MAI-AWGN channel, which can significantly reduce the co-channel interference responsible for capacity decline of a CDMA system. Third, the proposed CDMA architecture is able to offer a high bandwidth efficiency due to the use of its unique spreading modulation scheme and orthogonal carriers. Lastly, the proposed CDMA architecture is particularly suited to multirate signal transmission due to the use of an offset stacked spreading modulation scheme, which simplifies the rate-matching algorithm relevant to multimedia services and facilitates asymmetric traffic in up- and downlink transmissions for IP-based applications. Based on the above characteristics and the obtained results, it is concluded that the proposed CDMA architecture has a great potential for applications in future wideband mobile communications beyond 3G, which is expected to offer a very high data rate in hostile mobile channels     

A token circulation scheme for code assignment and cooperative transmission scheduling in CDMA-based UAV ad hoc networks

Code division multiple access (CDMA) ad hoc networks have been considered a promising multiple-channel networking architecture for connecting tactical platforms in battle fields. In this paper we consider a network of a swarm of unmanned aerial vehicles (UAVs) that are used in a tactical surveillance mission. The UAVs are assumed to have multiuser detection capability and form a CDMA-based ad hoc network. A token circulation scheme is proposed to conduct functions required at the medium access control layer including detection of hidden/lost neighbors, code assignment and schedule-based cooperative transmission scheduling. In the proposed scheme, a token continuously circulates around the network based on the “receive-forward” module. Through circulation of the token, each UAV can detect its hidden and/or lost neighbors in near real-time, assign codes enabling the spatial reuse of code channels without incurring code collision, and schedule data transmissions in a cooperative and distributed manner. In addition, the proposed scheme is able to take advantage of multiuser detection functionality and allows for simultaneous transmissions from multiple transmitters to a same receiver. The performance of the proposed token circulation scheme is evaluated, both analytically and through simulations. It is shown that the latency of the token is at most linearly proportional to the network size, and the average delay of a data packet increases with either the packet generation rate or the network size. The results also show that the proposed token circulation scheme is suitable for large-scale CDMA-based UAV ad hoc networks with even heavy network traffic load.     

A medium access control scheme for TDD-CDMA cellular networks with two-hop relay architecture

In this paper, we propose a multihop medium access control (mMAC) scheme for time division duplexing-code division multiple access (TDD-CDMA) cellular networks with two-hop relay architecture to support packet data transmission. The proposed mMAC is based on joint CDMA/PRMA (packet reservation multiple access) protocol and it includes BCH code selection, power control and multihop relaying. Simulation results reveal that cellular networks with two-hop relay architecture with the proposed mMAC scheme can substantially provide a good performance as well as larger cell coverage as compared to conventional TDD-CDMA single-hop cellular networks.     

无线mesh网络匿名通信机制研究

本文在对无线mesh网络深入研究的基础上,针对mesh网络环境下的隐私保护需求,提出在无线mesh网络下基于网络编码的匿名通信机制。该方案将多径路由技术与网络编码技术相结合,应用跨层协作机制降低了无线环境下的数据包重传,提高了网络的传输效率,保证了网络传输的可靠性。     

Green Architecture for Dense Home Area Networks Based on Radio-over-Fiber with Data Aggregation Approach

The high-density population leads to crowded cities. The future city is envisaged to encompass a large-scale network with diverse applications and a massive number of interconnected heterogeneous wireless-enabled devices. Hence, green technology elements are crucial to design sustainable and future-proof network architectures. They are the solutions for spectrum scarcity, high latency, interference, energy efficiency, and scalability that occur in dense and heterogeneous wireless networks especially in the home area network (HAN). Radio-over-fiber (ROF) is a technology candidate to provide a global view of HAN's activities that can be leveraged to allocate orthogonal channel communications for enabling wireless-enabled HAN devices transmission, with considering the clustered-frequency-reuse approach. Our proposed network architecture design is mainly focused on enhancing the network throughput and reducing the average network communications latency by proposing a data aggregation unit (DAU). The performance shows that with the DAU, the average network communications latency reduces significantly while the network throughput is enhanced, compared with the existing ROF architecture without the DAU.     

中兴通讯CDMA2000 ALL-IP灵活的组网解决方案

CDMA2000 ALL-IP产品推出了包含Ap接口在内的ALL-IP接口解决方案,丰富了网络架构.中兴通讯CDMA2000 ALL-IP产品技术先进,容量大,接口协议丰富,具有兼容性和演进性.描述了中兴通讯CDMA2000ALL-IP网络灵活的组网方案,主要针对CDMA网络演进到LMSD阶段后,分析实现BSC与核心网之间A接口分组传输后带来的一系列网络架构优势,组网方式的灵活.     

High data-rate packet communications for cellular networks usingCDMA: algorithms and performance

The advantages of code division multiple access (CDMA) for cellular voice have become well known, and IS-95-based systems have now been widely deployed. Attention is now focused on higher data-rate packet services for cellular systems. Although many packet multiple access schemes have been studied over the years, researchers have often studied single cell performance and ignored reuse. Moreover, direct sequence spread spectrum (DSSS) has been considered unsuitable for high data-rate packet multiple access since spreading limits the permitted data rates, DSSS requires large overhead (preambles) for acquisition and requires closed-loop power control. In this paper, we describe a scheme for high data-rate packet service using CDMA that addresses all of the above problems and has been standardized in Revision B of IS-95. A low rate fundamental code channel is maintained that eliminates the need for long preamble and provides closed-loop power control. Reuse is managed by the infrastructure through a “burst-level” admission control based on load and interference-level measurements at the base stations and mobiles. We report on the feasibility of such a burst-mode packet data service for cellular CDMA networks. The focus is not only on the performance of high data-rate users, but also on the impact on voice users sharing the CDMA band. We propose a multitiered performance analysis methodology consisting of a mix of static simulations, dynamic simulations at different time scales, and analytic methods to address the various feasibility issues: impact on coverage; capacity; power control; and effectiveness of burst admission algorithms. Based on the current study, we can conclude that the proposed approach is well suited for third-generation wideband CDMA systems being considered for standardization throughout the world     

基于预测的机会式网络编码

针对理论网络编码在实际应用上的缺陷,以及现有机会式网络编码完全依赖于消息偷听导致应用场合的局限性,以完全不同于网络编码优化问题的思路,提出了基于预测的机会式网络编码的方法。其主要思想是：基于网络流量的自相似性,利用EMD（empirical mode decomposition, 经验模式分解）和ARMA（自回归滑动平均）预测下一个报文的到达时间,综合计算编码时间、为了编码而等待的时间、传输时间等要素,从而决定是否编码。推导出了网络编码在不同情况下要实现吞吐量正增益可以等待的时间上界。仿真实验结果显示,在吞吐量上,提出的方法相对于理论网络编码平均提高15%左右,相对于当前的存储转发平均提高21%左右。在提高吞吐量的基础上,提出方法也可有效地降低网络的能量消耗。     

Packet CDMA versus dynamic TDMA for multiple access in anintegrated voice/data PCN

A comparative evaluation of dynamic time-division multiple access (TDMA) and spread-spectrum packet code-division multiple access (CDMA) approaches to multiple access in an integrated voice/data personal communications network (PCN) environment are presented. After briefly outlining a cellular packet-switching architecture for voice/data PCN systems, dynamic TDMA and packet CDMA protocols appropriate for such traffic scenarios are described. Simulation-based network models which have been developed for performance evaluation of these competing access techniques are then outlined. These models are exercised with example integrated voice/data traffic models to obtain comparative system performance measures such as channel utilization, voice blocking probability, and data delay. Operating points based on typical performance constraints such as voice blocking probability 0.01 (for TDMA), voice packet loss rate 10^-3 (for CDMA), and data delay 250 ms are obtained, and results are presented     

无线网络中基于机会网络编码的加权广播重传

在无线广播网链路状态不同和丢包率高的条件下,基于机会网络编码的数据分发策略面临传输效率低和计算复杂度高的问题。针对这一问题,该文提出一种新的基于机会网络编码的加权广播重传(Weighted Opportunistic Network Coding Retransmission, WONCR)方案。该方案通过构建加权数据包分布矩阵(Weighted Packet Distribution Matrix, WPDM),在重传过程中采用新的调度算法进行编码数据包的选取,并将选取的数据包进行XOR编码后再重传。机会仿真结果表明,WONCR方案提高了传输效率,且计算开销较小,实现了无线广播网中高效、可靠的数据分发。     

VLSI implementation of a CDMA blind adaptiveinterference-mitigating detector

This paper presents the design and the main performance results of a single-ASIC implementation of the recently proposed extended complex-valued blind anchored interference-mitigating detector (EC-BAID) for code division multiple access (CDMA) transmission. Such a detector, which exhibits a remarkable robustness to multiple access interference, operates in blind mode, i.e., it only requires knowledge of the timing of the wanted user's signature code, and it is therefore very well-suited for integration into handheld single-user terminal demodulators. The implementation of the interference-mitigating detector is based on a patented optimized architecture which leads, in 0.25-μm CMOS technology, to a roughly 25 Kgate plus 23-Kbit RAM single-chip ASIC supporting chip rates up to 4 Mchip/s with a maximum internal clock frequency of 32.768 MHz. The main design drivers are thoroughly discussed, and the relevant performance results are compared to the theoretical behavior. A possible extension to multirate CDMA systems adopting orthogonal variable spreading factor (OVSF) sequences is also addressed     

On reducing delay in mobile data collection based wireless sensor networks

In a wireless sensor network, battery power is a limited resource on the sensor nodes. Hence, the amount of power consumption by the nodes determines the node and network lifetime. This in turn has an impact on the connectivity and coverage of the network. One way to reduce power consumed is to use a special mobile data collector (MDC) for data gathering, instead of multi-hop data transmission to the sink. The MDC collects the data from the nodes and transfers it to the sink. Various kinds of MDC approaches have been explored for different assumptions and constraints. But in all the models proposed, the data latency is usually high, due to the slow speed of the mobile nodes. In this paper, we propose a new model of mobile data collection that reduces the data latency significantly. Using a combination of a new touring strategy based on clustering and a data collection mechanism based on wireless communication, we show that the delay can be reduced significantly without compromising on the advantages of MDC based approach. Using extensive simulation studies, we analyze the performance of the proposed approach and show that the packet delay reduces by more than half when compared to other existing approaches.     

传感网中能量均衡高效的源位置隐私保护协议

针对无线传感网中现有信源匿名协议大都存在无法同时兼顾源位置匿名性、延迟和生存周期的问题,对数据混淆、虚假信息注入等方法在隐私性、网络性能等方面进行了分析,在此基础上首次提出了基于匿名量化动态混淆环的源位置隐私保护协议ADRing：以能量均衡消耗确保的动态混淆环以及相应基于区位象限的匿名度量化评估机制来高效地保护信源节点位置隐私。仿真实验结果表明,ADRing相比于现有协议能明显改善网络能耗和延迟均衡性,延长网络寿命,能满足网络节点对于数据分组匿名性和延迟的不同需求。     

Rate-Distortion Optimized Video Transmission Over DS-CDMA Channels with Auxiliary Vector Filter Single-User Multirate Detection

In this paper, we consider the rate-distortion optimized resource allocation for video transmission over multi-rate wireless direct-sequence code-division-multiple-access (DS-CDMA) channels. We consider the performance of transmitting scalable video over a multipath Rayleigh fading channel via a combination of multi-code multirate CDMA and variable sequence length multirate CDMA channel system. At the receiver, despreading is done using adaptive space-time auxiliary-vector (AV) filters. We propose a new interference cancelling design that uses just a single AV filter for single-user mutirate despreading. Our experimental results show that the proposed interference cancelling design has excellent performance in scalable video transmission over DS-CDMA systems that use a combination of multicode multirate and variable processing gain multirate CDMA. The proposed design takes advantage of the fact that single user's video data is transmitted using two spreading codes, one for the base layer and one for the enhancement layers, and of the fact that these spreading codes can have different processing gains. The proposed interference cancelling design is compared with two conventional single-user multirate CDMA receiver configurations, however now we use an AV filter rather than a simple matched filter. We also propose a resource allocation algorithm for the optimal determination of source coding rate, channel coding rate and processing gain for each scalable layer, in order to minimize the expected distortion at the receiver.     

Frame time-hopping fiber-optic code-division multiple access using generalized optical orthogonal codes

A new spreading technique for intensity modulation direct detection fiber-optic code-division multiple-access (FO-CDMA) communication systems is proposed. This new spreading technique is based on generalized optical orthogonal codes (OOC) with large cardinality and minimal degradation in performance when compared with a more optimum system, namely, an optical CDMA system using OOC with autocorrelation and cross-correlation value bounded by one, i.e., OOC (/spl lambda/=1). To obtain the performance of such systems, we use a communication scheme, namely, frame time-hopping (FTH)-CDMA with random coding. Systems with generalized OOC patterns and random time-hopping coding are close in structure and performance. Furthermore, the performance of such systems is near the performance of optical CDMA with optimum but low cardinality OOC (/spl lambda/=1), which further renders the practicality of the proposed technique with very large cardinality. Two new receiver structures for FO-CDMA, namely, chip-level detector with optimum comparator threshold and correlation receiver with an electrical hard limiter, are also proposed. The performance analysis for a binary pulse position FTH-FO-CDMA network is considered for the correlation receiver, chip-level detector, correlation receiver with an optical hard limiter, optimum receiver, and the two newly proposed receiver structures. The results also show that a chip-level detector with optimum comparator threshold is superior to a chip-level detector for received low signal powers, and predict that the performance of the correlation receiver with an electrical hard limiter is superior to all other considered receiver structures, e.g., requiring one third of transmission power to achieve a desired bit error rate when compared with other receiver structures.     

一种适用于虚拟机网络的数据包高效传输方法

为了提高数据包在云计算数据中心中基于虚拟机构成网络中的传输性能,提出了一种基于网络编码的高效数据包传输方法.基于网络编码机制,采用对传输过程中丢失数据包高效的编码组合策略,多个虚拟机终端可以在一次多播或广播传输中获取多个从交换机优先传输的数据包,因此,提出的方法可以提高基于虚拟机网络的多播及广播业务的数据包传输延迟,并提高多播及广播业务的网络吞吐量.仿真结果表明提出的方法在典型信道条件下均获得了较好的数据包传输时延及网络吞吐量性能.     

手持式无线双模音视频传输软件设计与实现

设计与实现了一种基于WCDMA和CDMA20001X手持式双模音视频传输终端.重点针对终端系统软件体系架构、软件功能模块、双模传输调度关键技术等方面进行设计与实现.搭建双模音视频传输监控测试平台,测试结果表明相比于单模传输系统,利用WCDMA和CDMA20001X两个无线网络进行数据传输,有效提高了系统性能.