| 1. |
- Abusubaih, Murad, et al.
(författare)
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A New Access Point Selection Policy for Multi-Rate IEEE 802.11 WLANs
- 2008
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Ingår i: International Journal of Parallel, Emergent and Distributed Systems. - : Taylor & Francis Group. - 1744-5760 .- 1744-5779. ; 23:4, s. 291-307
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Tidskriftsartikel (refereegranskat)abstract
- In wireless local area networks, often a station can potentially associate with more than one access point (AP). Therefore, a relevant question is which AP to select 'best' from a list of candidate ones. In IEEE 802.11, the user simply associates to the AP with the strongest received signal strength. However, this may result in a significant load imbalance between several APs. Moreover, the multi-rate flexibility provided by several IEEE 802.11 variants can cause low bit rate stations to negatively affect high bit rate ones and consequently degrade the overall network throughput. This paper investigates the various aspects of 'best' AP selection for IEEE 802.11 systems. In detail, we first derive a new decision metric which can be used for AP selection. Using this metric, we propose two new selection mechanisms which are decentralised in the sense that the decision is performed by each station, given appropriate status information of each AP. In fact, only few bytes of status information have to be added to the Beacon and Probe Response frames which does not impose significant overhead. We show that our mechanism improves mean quality of service of all stations and better utilises network resources compared to the conventional one implemented today in IEEE 802.11 devices. Also, the schemes are appealing in terms of stability and provide their performance improvement even for denser or lighter network configurations.
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| 2. |
- Abusubaih, Murad, et al.
(författare)
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An Inter-Access Point Coordination Protocol for Dynamic Channel Selection in IEEE802.11 Wireless LANs
- 2007
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Konferensbidrag (refereegranskat)abstract
- This paper presents and evaluates an Inter-Access Point Coordination protocol for dynamic channel selection in IEEE 802.11 WLANs. It addresses an open issue for the implementation of many distributed and centralized dynamic channel selection policies proposed to mitigate interference problems in Wireless LANs (WLANs). The presented protocol provides services to a wide range of policies that require different levels of coordination among APs by enabling them to actively communicate and exchange information. An Intra-Cell protocol that enables interaction between the AP and its accommodated stations to handle channel switching within the same cell is also presented.
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| 3. |
- Abusubaih, Murad, et al.
(författare)
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On Access Point Selection in IEEE 802.11 Wireless Local Area Networks
- 2006
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Ingår i: 31st IEEE Conference on Local Computer Networks, Proceedings 2006. - : IEEE conference proceedings. - 1424404193 ; , s. 879-886
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Konferensbidrag (refereegranskat)abstract
- In wireless local area networks often a station can potentially associate with more than one access point. Therefore, a relevant question is which access point to select "best" from a list of candidate ones. In IEEE 802.11, the user simply associates to the access point with the strongest received signal strength. However, this may result in a significant load imbalance between several access points, as some accommodate a large number of stations while others are lightly loaded or even idle. Moreover, the multi-rate flexibility provided by several IEEE 802.11 variants can cause low bit rate stations to negatively affect high bit rate ones and consequently degrade the overall network throughput. This paper investigates the various aspects of "best" access point selection for IEEE 802.11 systems. In detail, we first derive a decision metric the selection can be based on. Using this metric we propose two new selection mechanisms which are decentralized in the sense that the decision is performed by each station, given appropriate status information of each access point. In fact, only few bytes of status information have to be added to the beacon and probe response frames which does not impose significant overhead. In addition, we show that our mechanism improves station quality of service and better utilizes network resources compared to the conventional one implemented today in IEEE 802.11 devices.
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| 4. |
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| 5. |
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| 6. |
- Behboodi, Arash, et al.
(författare)
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Interference Effect on Localization Solutions : Signal Feature Perspective
- 2015. - 10
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Ingår i: 2015 IEEE 81st Vehicular Technology Conference (VTC Spring). - 9781479980888
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Konferensbidrag (refereegranskat)abstract
- We study the effect of interference on localization algorithms through the study of the interference effect on signal features that are used for localization. Particularly, the effect of interference on packet-based Received Signal Strength Indicator (RSSI), reported by IEEE 802.11 and IEEE 802.15.4 technologies, and on Time of Flight (ToF), reported by IEEE 802.15.4 technology, is studied using both theoretical discussions and experimental verifications. As for the RSSI values, using an information theoretic formulation, we distinguish three operational regimes and we show that the RSSI values, in dBm, remain unchanged in the noise-limited regime, increase almost linearly with interference power in dBm in the interference-limited regime and cannot be obtained due to packet loss in the collision regime. The maximum observable RSSI variation is dependent on the transmission rate and Signal to Noise Ratio (SNR). We also show that ToF is, interestingly, decreased under interference which is caused in the symbol synchronization procedure at the receiver. After providing the experimental results, we discuss how the localization algorithms are affected by interference.
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| 7. |
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| 8. |
- Bohge, Mathias, et al.
(författare)
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A New Optimization Model for Dynamic Power and Sub-Carrier Allocations in Packet-Centric OFDMA Cells
- 2007
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Ingår i: Frequenz. - : FACHVERLAG SCHIELE SCHON. - 0016-1136 .- 2191-6349. ; 61:1-2, s. 35-38
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that applying dynamic resource allocation to down-link transmissions of OFDMAsystems provides a significant performance increase, by taking advantage of diversity effects. In order toquantify the maximum possible gain achievable by applying dynamic mechanisms, several optimizationproblems have been suggested for studying a dynamic system's optimal behaviour. However, so far theseoptimization approaches do not take sophisticated system requirements into account, as there are differentpacket-arrival processes, buffering constraints, scheduling policies, as well as QoS requirements per serviceclass. In this paper we present a new optimization model that is based on a packet-centric system view andincludes the system requirements mentioned above. We compare the performance results of the conventionaland the new approach and study the impact of dynamic power allocation in both cases.
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| 9. |
- Bohge, Mathias, et al.
(författare)
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Dynamic Resource Allocation in OFDM Systems : An Overview of Cross-Layer Optimization Principles and Techniques
- 2007
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Ingår i: IEEE Network. - : IEEE Communications Society. - 0890-8044 .- 1558-156X. ; 21:1, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e., policies) potentially provide significant performance gains for various systems. In this article we review several aspects of cross-layer system optimization regarding wireless OFDM systems. We discuss basic optimization models and present selected heuristic approaches realizing cross-layer policies by means of dynamic resource allocation. Two specific areas are treated separately: models and dynamic approaches for single transmitter/receiver pairs (i.e., a point-to-point communication scenario) as well as models and approaches for point-to-multipoint communication scenarios (e.g., the downlink of a wireless cell). This article provides basic knowledge in order to investigate future OFDM cross-layer-optimization issues.
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| 10. |
- Bohge, Mathias, et al.
(författare)
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Optimal Soft Frequency Reuse and Dynamic Sub-carrier Assignments in Cellular OFDMA Networks
- 2010
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Ingår i: European transactions on telecommunications. - : Wiley. - 1124-318X .- 2161-3915. ; 21:8, s. 704-713
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Tidskriftsartikel (refereegranskat)abstract
- Soft frequency reuse (SFR) is a common technique for co-channel interference (CCI) mitigation in cellular OFDMA networks. The performance of such networks significantly depends on the configuration of the power profiles that implement the soft frequency reuse patterns. In this paper, we investigate the performance of static soft frequency reuse by comparing it against the optimal case, in which a central entity optimally distributes power among the users of the network. It is shown that there is a significant performance gap between both approaches, which needs to be filled by adaptive SFR mechanisms. Moreover, we show that the achievable gain of static SFR is small in a system that is able to optimally decide on terminal/sub-carrier assignments.
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