Optimal Resource Allocation for Data Service in CDMA Reverse Link

The optimal resource allocation policy is studied for non-real-time users in CDMA reverse link. The resource allocation policy of interest includes channel coding, spreading gain control and power allocation under the conventional receiver operation. The constraints in the optimization include peak transmit power of the mobile station, total received power at the base station and QoS in the form of minimum SINR for each user. The coding and spreading gain control can be separated from the power allocation strategy. Our results show that the optimal power allocation policy depends on the objective function: a greedy policy is optimal to maximize the sum of throughput from each user, whereas a fair policy is optimal to maximize the product of throughput from each user. A unified approach is taken to derive the optimal policies, and it can also be applied to other power allocation problems in CDMA reverse link. Numerical results of the channel capacity are presented for both objectives along with the effect of QoS constraints.     

Efficient Design of Voice Carrying Fixed-Network Links in CDMA Mobile Communication Systems

Code Division Multiple Access (CDMA) technology is gaining momentum as the preferred wireless system for the next generation Personal Communication Systems (PCS). In CDMA systems, voice is encoded and packaged in variable length packets that are transported between the mobile station and the switching center. Although the packetization provides a great flexibility in resource allocation, it poses a Quality of Service (QoS) problem on voice. In this paper, we discuss link dimensioning for a typical CDMA system. We consider a T1/E1 link between a CDMA Basestation Transceiver System (BTS) and the Base Station Controller (BSC). Traffic from various voice sources is subject to a framing scheme, which presents a semi-periodic batch input at the T1/E1 interface cards. We analyze the resulting queuing system using discrete-time analysis and large deviations theory and verify our results by simulation. We provide results for the minimum link capacity needed to support a given number of CDMA voice sources. Our results show the potential statistical gain that can be achieved by voice packetization for all practical values of link capacities.     

宏分集对于CDMA系统前向容量的影响

宏分集可以有效地克服大尺度衰落的影响.对于CDMA反向信道而言,采用宏分集可以有效地改善信道质量并提高反向容量.与此相比,有关宏分集对CDMA前向信道的影响的研究则并不多见.本文深入分析了多天线宏分集下的CDMA系统前向容量并发现,在传统CDMA系统中,无论采用何种功率分配方案,宏分集都会导致前向容量损失.在分析容量损失原因的基础上,我们进一步提出了一种新的发送分集方案.在该方案下,前向容量不仅得到较大的提高,而且会随着参与宏分集的基站数目的增多进一步增大.     

A dynamic resource allocation scheme for delay-constrained multimedia services in CDMA 1/spl times/EV-DV forward link

CDMA2000 1/spl times/EV-DV has been proposed as one of the global standards of third-generation (3G) networks, which adopts TDM/CDM and adaptive modulation and coding (AMC) techniques to enhance the data rate. The current CDMA2000 1/spl times/EV-DV standard specifies all possible combinations of system parameters, but there is no any further specification in the standard on how to dynamically change the system parameters to support the quality-of-service (QoS) requirements imposed by the upper-layer applications. In the meantime, one of the major deficiencies of previous research work done in this area is that they all are based on the channel models of physical layer such as Rayleigh model, which is unable to capture the link-layer QoS parameters such as queueing delay. Since the dynamic resource allocation usually resides in the data link layer, a wireless channel model at the link layer would be desirable to handle the QoS requirements. In this paper, we develop a dynamic resource allocation scheme using the effective capacity link model to support delay-bounded multimedia services in CDMA2000 1/spl times/EV-DV networks. Extensive simulations have been set up and the simulation results show that the proposed dynamic resource allocation scheme significantly improves the delay and throughput performance for all types of application traffic with various QoS requirements.     

A simple performance/capacity analysis of multiclass macrodiversityCDMA cellular systems

Multiclass CDMA systems, which support multiple services with various quality of service (QoS) requirements, are studied. The focus is on the reverse link capacity and application of macrodiversity with maximal ratio combining (MMRC), where the signals from each mobile station (MS) are received by multiple base stations (BSs) and coherently combined. A simple analytical solution is first derived for the multiclass reverse link carrier-to-interference ratio (CIR). Using this CIR solution, a simple capacity analysis is developed in terms of the QoS requirements. Finally, the analysis is fully supported by simulation results     

多业务类分层结构CDMA系统功率控制研究

针对不同QoS要求的多业务类提供支持的分层结构CDMA系统的功率控制进行了研究，给出了该系统的一种功率控制算法。通过对反向链路运用HMRC方法，得到了一种支持多业务类的分层结构CDMA系统中反向链路CIR的简单分析方案和系统容量分析方法。     

CDMA/TDD移动通信系统的一种信道分配方案

未来的CDMA/TDD移动通信系统中存在话音和上下行链路业务量不等的数据业务,使传统的上下行等容量的信道分配方案不再适应业务的要求。提出了一种CDMA/TDD移动通信系统中上下行链路业务量不等时,信道资源分配方案。仿真结果表明,该方案可大大提高系统业务容量。     

VoIP over cdma2000 1xEV-DO revision A

In this article we analyze performance of VoIP services over 1xEVDO-Revision A (DO-Rev A) networks and show that high-quality VoIP with unconstrained mobility and high capacity can be achieved. Together with quality of service (QoS) requirements, we emphasize practical issues such as mobility, degradation of feedback-channel quality, and packet overheads. Novel techniques are presented for voice processing such as smart blanking and adaptive dejitter playback buffer with time warping. These techniques help to meet QoS constraints to achieve a circuit-like voice quality while improving overall capacity. Detailed end-to-end simulations are presented and system capacity is analyzed under the QoS and system stability constraints. We claim that DO-Rev A can provide VoIP capacity comparable to circuit-switched cellular CDMA technologies (e.g., IS-2000) and simultaneously carry significant amount of other types of traffic such as non-delay sensitive applications and downlink multicast.     

Hierarchical SIR and rate control on the forward link for CDMA datausers under delay and error constraints

We study the signal-to-interference ratio (SIR) and rate control for code division multiple access (CDMA) data users on the forward link under average or peak power constraints. The quality of service (QoS) for data users is specified by delay and error rate constraints as well as a family of utility functions representing the throughput and fairness among the data users. It is found that the optimal SIR and rate control algorithm has a hierarchical structure which can be easily implemented in a distributed manner. The SIR targets can be adjusted independently by the mobiles using information specific to the individual users. The data rates can be adjusted jointly by the base station based on limited feedback from the mobiles. We also propose a two-level iteration algorithm for both the mobile and the base station to efficiently compute the SIR and data rates. Our results show that a flexible tradeoff between total system throughput (sum of rates achieved) and fairness (similarity in data rates) can be achieved by choosing appropriate utility functions used in this scheme     

Macrodiversity power control in hierarchical CDMA cellular systems

Hierarchical code division multiple access (CDMA) cellular systems, consisting of macrocells with underlying microcells, are studied. We seek power control schemes which will allow both hierarchical layers to share the same spectrum. For the reverse link, hierarchical maximal ratio combining (HMRC) is applied where each mobile station (MSs) is received and coherently combined by base stations (BSs) in both layers. For the forward link, selective transmit diversity (STD) is applied where each BS provides multiple transmit paths for MSs to choose. We show that both HMRC and STD are effective in hierarchical CDMA architectures. We conclude that hierarchical architectures are a viable solution for improving CDMA cellular system capacity, and a significant performance gain can be achieved without assigning disjoint spectrum between the layers, by utilizing macrodiversity schemes such as HMRC and STD     

多业务蜂窝CDMA系统中的呼叫接纳控制策略

基于码分多址(CDMA)技术的第三代(3G)移动通信系统将支持多种业务传输,有效的呼叫接纳控制策略将使系统在满足各类业务不同QoS要求的同时,能够为更多的用户提供服务,该文首先分析了多业务蜂窝CDMA系统的剩余容量与QoS约束间的关系,接着提出了适用于任意多类业务环境、基于信号干扰比(SIR)测量的两种呼叫接纳控制策略,局部策略与全局策略,并通过大量计算机仿真研究了两种策略在业务均匀分布和非均匀分布环境下的性能,仿真结果表明,在两种业务分布情况下,全局策略的性能部优于局部策略。     

QoS-Driven Jointly Optimal Subcarrier Pairing and Power Allocation for Decode-and-Forward OFDM Relay Systems

In this paper, we investigate the quality-of-service (QoS) driven subcarrier pairing and power allocation for two-hop decode-and-forward (DF) OFDM relay systems. By integrating the concept of effective capacity, our goal is to maximize the system throughput subject to a given delay-QoS constraint. Based on whether the destination can receive the signal transmitted by the source, we consider two scenarios, i.e. OFDM DF relay systems without diversity and OFDM DF relay systems with diversity, respectively. For OFDM DF relay systems without diversity, we demonstrate that the jointly optimal subcarrier pairing and power allocation can be implemented with two separate steps. For OFDM DF relay systems with diversity, we propose an iterative algorithm to achieve jointly optimal subcarrier pairing and power allocation. Furthermore, we find that the analytical results show different conclusions for the two types of OFDM relay systems. For OFDM relay systems without diversity, the optimal power allocation depend on not only the channel quality of subcarriers but also the delay QoS constraints, while the optimal subcarrier pairing just depends on the channel quality of subcarriers. For OFDM relay systems with diversity, both the optimal subcarrier pairing and power allocation depend on the channel quality of subcarriers and the delay QoS constraints. Simulation results show that our proposed scheme offers a superior performance over the existing schemes.     

Optimal sequences, power control, and user capacity of synchronousCDMA systems with linear MMSE multiuser receivers

There has been intense effort in the past decade to develop multiuser receiver structures which mitigate interference between users in spread-spectrum systems. While much of this research is performed at the physical layer, the appropriate power control and choice of signature sequences in conjunction with multiuser receivers and the resulting network user capacity is not well understood. In this paper we will focus on a single cell and consider both the uplink and downlink scenarios and assume a synchronous CDMA (S-CDMA) system. We characterize the user capacity of a single cell with the optimal linear receiver (MMSE receiver). The user capacity of the system is the maximum number of users per unit processing gain admissible in the system such that each user has its quality-of-service (QoS) requirement (expressed in terms of its desired signal-to-interference ratio) met. This characterization allows one to describe the user capacity through a simple effective bandwidth characterization: users are allowed in the system if and only if the sum of their effective bandwidths is less than the processing gain of the system. The effective bandwidth of each user is a simple monotonic function of its QoS requirement. We identify the optimal signature sequences and power control strategies so that the users meet their QoS requirement. The optimality is in the sense of minimizing the sum of allocated powers. It turns out that with this optimal allocation of signature sequences and powers, the linear MMSE receiver is just the corresponding matched filter for each user. We also characterize the effect of transmit power constraints on the user capacity     

Optimal Resource Allocation for Spectrum Sensing Based Cognitive Radio Networks with Statistical QoS Guarantees

Resource allocation under spectrum sensing based dynamic spectrum sharing strategy is a critically important issue for cognitive radio networks (CRNs), because they need to not only satisfy the interference constraint caused to the primary users (PUs), but also meet the quality-of-service (QoS) requirements for the secondary users (SUs). In this paper, we develop the optimal spectrum sensing based resource allocation scheme for the delay QoS constrained CRNs. Specifically, we aim at maximizing the maximum constant arrival rate of the SU that can be supported by the time-varying service process subject to the given statistical delay QoS constraint. In our derived power allocation scheme, not only the average transmit and interference power constraints are considered, but also the impact of the PUs?? transmission to the CRNs and the PUs?? spectrum-occupancy probability are taken into consideration. Moreover, the spectrum sensing errors are also taken into consideration. Simulation results show that, (1) the effective capacity of the secondary link decreases when the statistical delay QoS constraint becomes stringent; (2) given the QoS constraint, the effective capacity of the secondary link varies with the interference power constraint and the SNR of the primary link.     

An FDD wideband CDMA MAC protocol with minimum-power allocation and GPS-scheduling for wireless wide area multimedia networks

A frequency division duplex (FDD) wideband code division multiple access (CDMA) medium access control (MAC) protocol is developed for wireless wide area multimedia networks. In order to reach the maximum system capacity and guarantee the heterogeneous bit error rates (BERs) of multimedia traffic, a minimum-power allocation algorithm is first derived, where both multicode (MC) and orthogonal variable spreading factor (OVSF) transmissions are assumed. Based on the minimum-power allocation algorithm, a multimedia wideband CDMA generalized processor sharing (GPS) scheduling scheme is proposed. It provides fair queueing to multimedia traffic with different QoS constraints. It also takes into account the limited number of code channels for each user and the variable system capacity due to interference experienced by users in a CDMA network. To control the admission of real-time connections, a connection admission control (CAC) scheme is proposed, in which the effective bandwidth admission region is derived based on the minimum-power allocation algorithm. With the proposed resource management algorithms, the MAC protocol significantly increases system throughput, guarantees BER, and improves QoS metrics of multimedia traffic.     

Performance analysis of cellular CDMA networks overfrequency-selective fading channel

An effect of multipath fading on the performance of a cellular code-division multiple-access (CDMA) system is analyzed in this paper. A wide-sense stationary uncorrelated scattering (WSSUS) channel model and the coherent binary phase-shift keying (BPSK) with asynchronous direct-sequence (DS) spreading signal are assumed in the analysis. The average error probability for both the forward link and reverse link of a cellular CDMA system over a frequency-selective fading channel using a conventional correlation-type receiver and RAKE receiver are derived. The impact of imperfect power control and channel capacity of a cellular CDMA system is also investigated. The closed forms of average error probability derived in the paper can save a lot of computation time to analyze the performance and channel capacity of a cellular CDMA system. The analytical results show that the performance and maximum transmission rate of cellular CDMA systems degrade with an increase in the number of simultaneous users and the number of interfering cells. The signal-to-interface ratio (SIR) for the reverse link derived in this paper can directly describe the interrelationships among a number of paths, number of users, number of interfering cells, fading factors, and maximum variation of a received unfaded signal     

Multirate optical fast frequency hopping CDMA system using powercontrol

This paper addresses the problem of real-time multimedia transmission in fiber-optic networks using code division multiple access (CDMA). We present a multirate optical fast frequency hopping CDMA (OFFH-CDMA) system architecture using fiber Bragg gratings (FBGs). In addition, we argue that, in multimedia applications, different services have different quality of service (QoS) requirements; hence, the user only needs to use the minimum required power to transmit the signal, such that the required signal-to-interference ratio (SIR) is met. We show that a variable bit rate optical communication system with variable QoS can be implemented by way of power control with great efficiency. Present-day multirate optical CDMA systems concentrate on finding the code structure that supports a variable rate system, neglecting the importance of the transmission power of active users on the multiple access interference (MAI) and, therefore, on the system capacity. We assign different power levels to each rate through a power control algorithm using variable optical attenuators, which minimizes the interference and, at the same time, provides variable QoS constraints for different traffic types. Although we are using a code family that preserves good correlation properties between codes of different lengths, simulations show a great improvement in the system capacity when power control is used     

Radio resource management for cellular CDMA systems supporting heterogeneous services

A novel radio resource management (RRM) scheme for the support of packet-switched transmission in cellular CDMA systems is proposed by jointly considering the physical, link, and network layer characteristics. The proposed resource management scheme is comprised of a combination of power distribution, rate allocation, service scheduling, and connection admission control. Power distribution allows individual connections to achieve their required signal-to-interference-plus-noise ratio, while rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness; of the packet generation process. At the link layer, a packet scheduling scheme is developed based on information derived from power distribution and rate allocation to achieve quality of service (QoS) guarantee. Packet scheduling efficiently utilizes the system resources in every time slot and improves the packet throughput for non-real-time traffic. At the network layer, a connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed. The CAC scheme makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service performance, in terms of new connection blocking probability, HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.     

Traffic Aided Uplink Opportunistic Scheduling with QoS Support in Multiservice CDMA Networks

In this letter, we address the problem of resource allocation with efficiency and quality of service (QoS) support in uplink for a wireless CDMA network supporting real‐time (RT) and non‐realtime (NRT) communication services. For RT and NRT users, there are different QoS requirements. We introduce and describe a new scheme, namely, traffic aided uplink opportunistic scheduling (TAUOS). While guaranteeing the different QoS requirements, TAUOS exploits the channel condition to improve system throughput. In TAUOS, the cross‐layer information, file size information, is used to improve fairness for NRT users. Extensive simulation results show that our scheme can achieve high system throughput in uplink wireless CDMA systems, while guaranteeing QoS requirements.     

基于对偶分解的OFDMA系统资源分配算法

该文针对多业务OFDMA系统资源分配问题,建立了考虑业务服务质量、数据到达、系统约束的最优化问题。分析了不同业务的速率约束、延时约束和队列长度之间的关系,并利用对偶分解方法将原问题分解为若干独立子问题,分别得到了最优资源块与最优功率分配规则,进而提出了基于对偶分解的最优资源分配算法。仿真结果表明,该算法在业务违反概率较低、公平性较好、算法复杂度略有上升的情况下,可以实现非实时业务吞吐量最大化。