IEEE 802.16 Mesh Schedulers: Issues and Design Challenges

UAE Univ., Al-Ain
IEEE Network (Impact Factor: 2.54). 02/2008; 22(1):58 - 65. DOI: 10.1109/MNET.2008.4435904
Source: IEEE Xplore


IEEE 802.16 mesh mode defines three types of resource scheduling: coordinated centralized, coordinated distributed, and uncoordinated distributed. While the standard defines the required procedures and messages for each scheduler, it does not offer encouraging means to provide performance, reliability, or QoS. In this article we outline the issues of IEEE 802.16 mesh schedulers. We also survey representative proposals and qualitatively evaluate them against these issues. More critically, we identify key challenges that have not been addressed so far in the literature to motivate work in this area of research.

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Available from: Najah Abu Ali, Mar 06, 2014
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    • "The IEEE 802.16 standard supports three types of scheduling mechanisms: centralized scheduling, coordinated distributed scheduling (CDS) and uncoordinated distributed scheduling. These mechanisms are based on time division multiple access (TDMA) frame structures [7]. Each frame is composed of a control subframe and a data subframe of fixed length. "
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    ABSTRACT: IEEE 802.16 based wireless mesh networks (WMNs) are a promising broadband access solution to support flexibility, cost effectiveness and fast deployment of the fourth generation infrastructure based wireless networks. Reducing the time for channel establishment is critical for low latency/interactive applications. In this paper, we propose two modifications to the election based transmission timing (EBTT) mechanism used in the coordinated distributed scheduling (CDS) within the IEEE 802.16 standard, which makes use of the standardized signaling messages and formats. Simulation results show that our proposed modifications results in significantly reduced channel establishment delay - up to 75% with low neighborhood densities - over the standard, and at least 10% with high neighborhood densities. Moreover, the proposed mechanisms are also applicable for the three-hop extended neighborhood CDS when required.
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    • "Note that the value of λ i , for any frame i, is strictly equal to or larger than L Dmin , because nodes will always request time slots, regardless of having current data to send or not [1] [12]. If the scheduling process results in allocation that is larger than the available slots in the data subframe, the allocation can be either scaled down proportionally to bandwidth requests, or spanned over a long frame (two-frames) as explained in the standard [1]. "
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    ABSTRACT: The IEEE 802.16 standard, also known as WiMAX, defines flexible frame structures to support applications classified into different WiMAX traffic classes. The standard defines two types of scheduling to guarantee the quality of service (QoS) requirements of these applications - centralized and distributed. However, the standard does not specify how the frame can be dynamically partitioned among its centralized and distributed schedulers or uplink and downlink schedulers. Through efficient partitioning that dynamically adapts the partitioning based on demand, network can support more user applications with different QoS requirements, and hence increase the revenues of service providers. In this paper, we propose a novel and general dynamic frame partitioning scheme for IEEE 802.16 mesh and IEEE 802.16j multi-hop relay networks. The scheme uses a dynamic Markov model that studies the frame utilization over current frames to predict efficient partitions for future frames. Simulation results show that the proposed scheme improves average frame utilization and decreases packet dropping.
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    • "Firstly, the constraint is compatible with current standards. For example, the mesh mode in IEEE 802.16 standard only allows each link to transmit once in a frame [3]. Secondly, in real-world implementation, guard intervals are inserted between the transmissions of different users. "
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    ABSTRACT: This paper considers the problem of link scheduling with non-preemptive constraint in wireless mesh networks. In real-world implementation, there is often a constraint that a link can only transmit once and occupy consecutive time slots during a frame. We refer to it as the non-preemptive constraint. To date, only few scheduling algorithms in the literature has taken such constraint into consideration. In this paper, we show that optimal non-preemptive link scheduling (NPLS) problems are generally NP-hard and are provably harder to solve than link scheduling without such a constraint. To tackle the problem, a low-complexity list link scheduling (LLS) algorithm is proposed to approximate the optimal NPLS. Our analysis shows that with a randomly selected link-ordering list, throughput degradation of LLS compared to the optimal NPLS is bounded even in the worst case. By carefully constructing the link-ordering list, the performance of LLS can be further greatly improved. In this paper, we propose three schemes to construct link-ordering lists. The performance of the proposed schemes is evaluated through simulations.
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