CSMA-based Wireless Networks Research Articles

Dynamic Counter Angle-Based Broadcasting in CSMA-Based Wireless Networks

Dynamic Counter Angle-Based Broadcasting in CSMA-Based Wireless Networks

Utility Bounds of Joint Congestion and Medium Access Control for CSMA based Wireless Networks

In this paper, we study the problem of network utility maximization in a CSMA based multi-hop wireless network. Existing work in this aspect typically adopted continuous time Markov model for performance modelling, which fails to consider the channel conflict impact in actual CSMA networks. To maximize the utility of a CSMA based wireless network with channel conflict, in this paper, we first model its weighted network capacity (i.e., network capacity weighted by link queue length) and then propose a distributed link scheduling algorithm, called CSMA based Maximal-Weight Scheduling (C-MWS), to maximize the weighted network capacity. We derive the upper and lower bounds of network utility based on C-MWS. The derived bounds can help us to tune the C-MWS parameters for C-MWS to work in a distributed wireless network. Simulation results show that the joint optimization based on C-MWS can achieve near-optimal network utility when appropriate algorithm parameters are chosen and also show that the derived utility upper bound is very tight.

Energy-Optimum Throughput and Carrier Sensing Rate in CSMA-Based Wireless Networks

We propose a model for the energy consumption of a node as a function of its throughput in a wireless CSMA network. We first model a single-hop network, and then a multi-hop network. We show that operating the CSMA network at a high throughput is energy inefficient since unsuccessful carrier sensing attempts increase the energy consumption per transmitted bit. Operating the network at a low throughput also causes energy inefficiency because of increased sleeping duration. Achieving a balance between these two opposite operating regimes, we derive the energy-optimum carrier-sensing rate and the energy-optimum throughput which maximize the number of transmitted bits for a given energy budget. For the single-hop case, we show that the energy-optimum total throughput increases as the number of nodes sharing the channel increases. For the multi-hop case, we show that energy-optimum throughput decreases as the degree of the conflict graph corresponding to the network increases. For both cases, the energy-optimum throughput reduces as the power required for carrier-sensing increases. The energy-optimum throughput is also shown to be substantially lower than the maximum throughput and the gap increases as the degree of the conflict graph increases for multi-hop networks.

Independent links: A new approach to increase spatial reuse in wireless networks

This paper explores a new method of improving the performance of CSMA-based wireless networks. The main proposal is to achieve a higher degree of spatial reuse by increasing the number of independent links. A pair of links is independent if the mutual interference generated by simultaneous transmissions on these links can be tolerated by all devices involved. In this paper, we derive the conditions for independence of links, and show that maximizing their number in a network is a complex problem. These insights were used to develop an efficient and decentralized heuristic, whose performance is evaluated by simulation. This mechanism outperforms recent literature proposals on a large number of random topologies.

CSMA 기반 무선 애드 혹 네트워크에서 반송파 감지 반경의 반복적 근사 기법

최근 CSMA가 많은 무선 환경에서 적용됨에 따라 CSMA 기반의 우선 네트워크의 성능을 높이기 위한 다양한 통계적 분석이 수행되고 있다. 그러나 이러한 노력에도 불구하고 여전히 CSMA가 가지고 있는 작위적 특성은 네트워크의 분석을 어렵게 만들고 있다. 기존의 많은 연구들은 대규모 CSMA 네트워크의 통계적 분석에서 노드의 반송파 감지 기능을 표현하기 위해 반송파 감지 반경을 도입하여 사용해 왔다. 그러나 반송파 감지 반경은 노드의 전송 여부에 따른 노드 간 간섭효과를 고려하지 않기 때문에 간섭이 큰 채널 환경에 적용되는 경우 분석 오류를 피하기 어렵다. 본 연구에서는 이러한 문제점을 해결하고자 노드 간 간섭효과를 고려한 물리적 모델 기반의 반송파 감지 반경을 유도하는 알고리즘을 제안한다. 이를 위해 대규모 CSMA 네트워크에서의 반송파 감지 동작 특성과 이에 따른 간섭효과를 분석하고, 분석 결과를 토대로 물리 모델에 근사된 반송파 감지 반경을 찾기 위한 감지 반경의 반복적 근사 기법을 제안한다. 제안된 알고리즘의 적합성을 확인하기 위해 모의실험을 통해 제안된 감지 반경을 이용해 다양한 채널 환경에서 유도된 총 간섭 모델의 정확성을 비교 분석하였다. Recently, as CSMA technique has been increasingly adopted in various wireless networks, extensive researches to analyze the statistical characteristics of CSMA-based wireless networks have been done. Despite the ongoing efforts, there still remain many difficulties in the analysis because of unexpectable operational behavior of CSMA. Previous literature studying CSMA networks used the concept of the carrier sensing radius to reflect the carrier sensing function. However, since the carrier sensing radius based on the protocol model is not affected by the aggregate interference from other nodes, the derived statistical models cannot avoid approximation errors especially if the network is under high interference. In this paper, we propose an algorithm to derive the carrier sensing radius considering the physical model, where the carrier sensing radius reflecting the aggregate interference is found. For the purpose of this, we analyze the aggregate interference model and the behavior of CSMA function. Based on the analysis, we propose an iterative approximation algorithm for the physical carrier sensing radius. Extensive simulations and results show that the proposed algorithm can contribute to considerably reduce the statistical modeling error of a CSMA network under various channel conditions.

Analytical Modeling and Performance Analysis of Flooding in CSMA-Based Wireless Networks

Although different broadcasting techniques are widely deployed in wireless networks, there are limited comprehensive analytical frameworks to evaluate the performance of such schemes. In this paper, based on a rigorous theoretical analysis, upper bounds on the network coverage and the total number of transmissions (corresponding to network energy consumption) of flooding and its popular variant probabilistic flooding are derived. The analysis is performed for a static multihop ad hoc wireless network when the network is in saturated condition. To consider a realistic medium-access control (MAC) layer algorithm, successful signal reception is based on the protocol model, and nodes employ carrier-sense multiple access. Based on the concept of marked point process, two different approaches, i.e., hop based and time based, are proposed. In the hop-based approach, an upper bound on network coverage and energy consumption is derived for any serving policy and queuing delay that broadcasted packets experience. This approach can be easily extended to multiple-source scenarios. The time-based approach is appropriate for the case of known service policy and queuing delay, and it predicts the time-domain behavior of the broadcasting schemes, as well as other mentioned parameters. We show that the two bounds are very close to each other. The first approach has less complexity, whereas the second approach provides a tighter bound. As an interesting result, we analytically demonstrate that the disjoint analysis of MAC and network layers provides a much simpler solution, whereas the obtained results are also upper bounds on the network coverage. Simulation results validate our analytical model and demonstrate its tightness for real scenarios.

A Modified p-Persistent Model for CSMA-Based Wireless Networks with Pseudo Capture Effect

The existing carrier sensing multiple access (CSMA) based wireless networks cannot realize the capture effect functionality. Consequently, transmitters within the physical carrier sensing (PCS) range of a receiver cause interference to its reception, which is referred to as the pseudo capture effect. Such interference severely degrades the system performance because the default PCS range is usually quite large. Therefore the PCS range should be adjusted to reduce the packet loss caused by pseudo capture effect. In order to guide the optimal PCS range setting, a modified p-persistent model is proposed in this paper to investigate the throughput of CSMA-based networks considering pseudo capture effect. Simulation results show that the proposed model accurately evaluates the influence of pseudo capture effect. By utilizing the model, we observe that the optimal PCS range considering pseudo capture effect is smaller than the case without considering its impact.