Cross-layer Rate Control Research Articles

Cross-Layer Rate Control and Resource Allocation in Spectrum-Sharing OFDMASmall Cell Networks with Delay Constraints

In this paper, we present a dynamic resource management scheme for delay-aware applications in two-tier small-cell networks (SCNs). We propose the scheme of joint rate control at the transport layer and resource allocation at the physical layer to manage the cross-tier interference. The joint rate control and resource allocation scheme is designed to maximize the time-averaged sum capacity of small cell users in the SCN subject to each small cell user's delay constraint and an interference constraint imposed by the macrocell. By using the Lyapunov optimization technique, we develop a delay-guaranteed capacity optimal algorithm (DCOA) to obtain the optimal rate control and resource allocation decisions. We show that without prior knowledge of the data arrivals and channel statistics, DCOA achieves a capacity of SCN that can arbitrarily approach the optimal capacity achieved by the algorithm with the complete knowledge of data arrivals and channel statistics. Simulations results confirm the theoretical analysis on the performance of DCOA and also show the adaptiveness of DCOA.

Fair rate control for cognitive multi-channel wireless ad hoc networks

Multi-channel wireless ad hoc networks enhance network capacity with the use of available channels in parallel but should strike a balance between maintaining network connectivity and maximizing utilization of different channels. Also, a promising wireless multi-channel ad hoc network should be cognitive to interference from various wireless devices operating on industrial, scientific, and medical bands effectively by scavenging less loaded channels dynamically using periodic spectrum sensing and distributed channel selection algorithm. In this paper, we study cross-layer fair rate control problems for hybrid channel assignment-based multi-channel ad hoc networks in the cognitive context. We first identify two inherent constraints which are specific to multi-channel multi-radio wireless ad hoc networks and primary user interference. We then formulate a fair rate control problem by exploiting the network utility maximization framework and propose a price-based distributed solution. We investigate in detail the convergence property of the distributed solution via simulation on a grid topology. We also show its convergence in adaptation to the change in primary user interference in the cognitive context. We present a performance comparison study with a generic class of existing works in the literature.

Rate-Distortion Optimized Cross-Layer Rate Control in Wireless Video Communication

A wireless video communication system can be designed based on the rate-distortion (R-D) criterion, i.e., minimizing the end-to-end distortion (which includes quantization distortion and transmission distortion) subject to the transmission bit-rate constraint. The minimization can be achieved by adjusting the source encoding parameters and channel encoding parameters. This rate-distortion optimization (RDO) is usually done for each video frame individually in a real-time video communication system, e.g., video calls or videoconferencing. To achieve this, an accurate bit-rate model and distortion model for each frame can be used to reduce the RDO complexity. In this paper, we derive a source bit-rate model and quantization distortion model; we also improve the performance bound for channel coding under a convolutional code and a Viterbi decoder, and derive its performance bound under a Rayleigh block fading channel. Given the instantaneous channel condition, e.g., signal-to-noise ratio and transmission bit-rate constraint, we design an R-D optimized cross-layer rate control (CLRC) algorithm by jointly choosing quantization step size in source coding and code rate in channel coding. Experimental results show that our proposed R-D models are more accurate than the existing R-D models. Experimental results also showed that the rate control under our models has more stable R-D performance than the existing rate control algorithms; using the channel estimation, CLRC can further achieve remarkable R-D performance gain over that without channel estimation. Another important result is that the subjective quality of our CLRC algorithm is much better than the existing algorithms due to its intelligent reference frame selection.

A Cross-layer Rate Control Method for MIMO-WLAN

针对下一代无线局域网高速率演进的要求，该文提出一种跨层的多输入多输出(MIMO)系统速率控制算法。首先分析了保证业务误码率的物理层吞吐率最大的速率控制算法存在的不足；然后结合自适应调制编码技术，实现了基于预测的MAC(Media Access Control)层吞吐率最大的跨层速率控制算法。仿真和分析表明算法可以取得近似优化的速率选择结果，能够保证业务的误码率性能，提高业务的吞吐率。该文的算法计算简单、预测准确、运行高效，不仅可以实现闭环速率控制，还可用于帧重传和多业务调度等应用的速率控制。

Cross-Layer Rate Control, Routing and Scheduling Design for Multicast with Network Coding in Ad Hoc Networks

Network coding is a powerful coding technique that has been proved to be very effective in achieving the maximum multicast capacity. It is especially suited for new emerging networks such as ad-hoc and sensor networks. In this paper, we develop a distributed rate control algorithm for multicast session in ad hoc networks. With random network coding, the algorithm can be implemented in a distributed manner, and work at transport layer to adjust source rates and at network layer to carry out network coding. The scheduling element of our algorithm is a dynamic scheduling policy. The stability of the resulted system is established, and simulation results are provided to support our conclusions.

A distortion-minimizing rate controller for wireless multimedia sensor networks

The availability of inexpensive CMOS cameras and microphones that can ubiquitously capture multimedia content from the environment is fostering the development of wireless multimedia sensor networks (WMSNs), i.e., distributed systems of wirelessly networked devices that can retrieve video and audio streams, still images, and scalar sensor data. A new cross-layer rate control scheme for WMSNs is introduced in this paper with a twofold objective: (i) maximize the video quality of each individual video stream; (ii) maintain fairness in the domain of video quality between different video streams. The rate control scheme is based on analytical and empirical models of video distortion and consists of a new cross-layer control algorithm that jointly regulates the end-to-end data rate, the video quality, and the strength of the channel coding at the physical layer. The end-to-end data rate is regulated to avoid congestion while maintaining fairness in the domain of video quality rather than data rate. Once the end-to-end data rate has been determined, the sender adjusts the video encoder rate and the channel encoder rate based on the overall rate and the current channel quality, with the objective of minimizing the distortion of the received video. Simulations show that the proposed algorithm considerably improves the received video quality with respect to state-of-the art rate control algorithms, without sacrificing on fairness.

Cross-layer rate control in wireless networks with lossy links: leaky-pipe flow, effective network utility maximization and hop-by-hop algorithms

We take a cross-layer design approach to study rate control in multihop wireless networks. Due to the lossy nature of wireless links, the data rate of a given flow becomes smaller and smaller along its routing path. As a result, the data rate received successfully at the destination node (the rate) is typically lower than the transmission rate at the source node (the injection rate). In light of this observation, we treat each flow as a leaky-pipe flow and introduce the notion of effective associated with the rate (not the injection rate) of each flow. We then explore rate control through network utility maximization (ENUM) in this study. Two network models are studied in this paper: (1) ENUM with link outage constraints with a maximum error rate at each link; (2) ENUM with path outage constraints where there exists an end-to-end outage requirement for each flow. For both models, we explicitly take into account the thinning feature of data flows and devise distributed hop-by-hop rate control algorithms accordingly. Our numerical examples corroborate that higher network utility and better fairness can be achieved by the ENUM algorithms than the standard NUM.

The Impact of Stochastic Noisy Feedback on Distributed Network Utility Maximization

The implementation of distributed network utility maximization (NUM) algorithms hinges heavily on information feedback through message passing among network elements. In practical systems the feedback is often obtained using error-prone measurement mechanisms and suffers from random errors. In this paper, we investigate the impact of noisy feedback on distributed NUM. We first study the distributed NUM algorithms based on the Lagrangian dual method, and focus on the primal-dual (P-D) algorithm, which is a single time-scale algorithm in the sense that the primal and dual parameters are updated simultaneously. Assuming strong duality, we study both cases when the stochastic gradients are unbiased or biased, and develop a general theory on the stochastic stability of the P-D algorithms in the presence of noisy feedback. When the gradient estimators are unbiased, we establish, via a combination of tools in Martingale theory and convex analysis, that the iterates generated by distributed P-D algorithms converge with probability one to the optimal point, under standard technical conditions. In contrast, when the gradient estimators are biased, we show that the iterates converge to a contraction region around the optimal point, provided that the biased terms are asymptotically bounded by a scaled version of the true gradients. We also investigate the rate of convergence for the unbiased case, and find that, in general, the limit process of the interpolated process corresponding to the normalized iterate sequence is a stationary reflected linear diffusion process, not necessarily a Gaussian diffusion process. We apply the above general theory to investigate stability of cross-layer rate control for joint congestion control and random access. Next, we study the impact of noisy feedback on distributed two time-scale NUM algorithms based on primal decomposition. We establish, via the mean ODE method, the convergence of the stochastic two time-scale algorithm under mild conditions, for the cases where the gradient estimators in both time scales are unbiased. Numerical examples are used to illustrate the finding that compared to the single time-scale counterpart, the two time-scale algorithm, although having lower complexity, is less robust to noisy feedback.

Cross-layer rate control, medium access control and routing design in cooperative VANET

In this paper, we address the rate control, the Medium Access Control (MAC) and the routing problem for cooperative Vehicular Ad-Hoc Network (VANET) in the framework of cross-layer design. At first, we introduce the cooperative communication conception to VANET, and propose an opportunistic cooperation strategy to improve the system performance. And then, we develop a cross-layer solution which consists of the link capacity detection with adjusting persistence probability at the MAC Layer, the flow rate control with the maximal utility at the Transport Layer and the routing design at the Network Layer. This proposal is designed in distributed manner in order to support a simple and efficient implementation for VANET. Furthermore, some practical issues, such as fairness and network cost, are presented for implementing the proposed solution and improving the system performance. Simulation results show that the proposed opportunistic cooperation strategy combined with joint control algorithm achieves the desired performance over VANET.

A Cross-Layer Rate Control Mechanism for Link-Adaptive Satellite Integrated Services

This paper presents a mechanism for dynamic rate control of satellite integrated services, based on a cross-layer approach, utilising link quality feedback from the satellite terminals. The mechanism, namely, satellite resource management system (SRMS) relies on the adaptive coding and modulation (ACM) capabilities of DVB-S2 in order to perform real-time adjustments on the physical, network and services layer and optimise the usage of satellite spectrum. The functionality of the SRMS is discussed along with its implementation in the frame of the IST IMOSAN Project. Simulation results are presented, involving modelled rain fading and prioritised heterogeneous services, which illustrate the efficiency of the proposed solution against current static transmission schemes.

Maximum lifetime rate control and random access in multi-hop wireless networks

Network lifetime and transmission quality are of paramount importance for rate control in an energy constrained multi-hop wireless network. It is known that they depend on mechanisms that span several protocol layers due to the existing interference across collision links and the energy constrained nature of wireless nodes. Although separate consideration of these issues simplifies the system design, it is often insufficient for wireless networks when the overall system performance is required. In this paper, we present a framework for cross-layer rate control towards maximum network lifetime and collision avoidance. The main contributions of this paper are twofold. First, although the link attainable rate is typically a non-convex and non-separable function of persistent probabilities, we prove the convergence of this cross-layer algorithm to the global optimum of joint congestion control and random access algorithm under the framework of nonlinear programming. Second, by adjusting a parameter in the objective function, we achieve the tradeoff between transmission quality and network lifetime. Simulations illustrate the desirable properties of the proposed algorithm, including convergence to the global optimum, better performance than the layered scheme, desirable tradeoff between transmission quality and network lifetime.

An optimization based approach for cross-layer design in wireless communication networks

In this talk we study the issue of cross-layer design for rate control in multihop wireless networks. We have developed an optimal cross-layered rate control scheme that jointly computes both the rate allocation and the stabilizing schedule that controls the resources at the underlying layers. However, the scheduling component in this optimal cross-layered rate control scheme has to solve a complex global optimization problem at each time, and is hence too computationally expensive for online implementation. Thus, we study the impact on the performance of cross-layer rate control if the network can only use an imperfect (and potentially distributed) scheduling component that is easier to implement. We study scenarios with both fixed number of users as well as when the number of users change due to arrivals and departures in the system. In each case, we establish desirable results on the performance bounds of cross-layered rate control with imperfect scheduling. Our cross-layered approach provides provably better performance bounds when compared with a layered approach (that does not design rate control and scheduling together). The insights drawn from our analyses also enable us to design a fully distributed cross-layered rate control and scheduling algorithm under a restrictive interference model.