This paper evaluates four mechanisms for providing service differentiation in IEEE 802.11 wireless LANs, the point coordinator function (PCF) of IEEE 802.11, the enhanced distributed coordinator function (EDCF) of the...
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ISBN:
(纸本)0769513212
This paper evaluates four mechanisms for providing service differentiation in IEEE 802.11 wireless LANs, the point coordinator function (PCF) of IEEE 802.11, the enhanced distributed coordinator function (EDCF) of the proposed IEEE 802.11e extension to IEEE 802.11, distributed fair scheduling (DFS), and Blackburst using the ns-2 simulator. The metrics used in the evaluation are throughput, medium utilization, collision rate, average access delay, and delay distribution for a variable load of real time and background traffic. The PCF performance is comparably low, while the EDCF performs much better. The best performance is achieved by Blackburst. The DFS provides relative differentiation and consequently avoids starvation of low priority traffic.
The phenomenal growths of group communications and QoS-aware applications over the Internet have respectively accelerated the development of two key technologies, namely, multicasting and differentiated services (Diff...
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The phenomenal growths of group communications and QoS-aware applications over the Internet have respectively accelerated the development of two key technologies, namely, multicasting and differentiated services (DiffServ). Although both are complementary technologies, the integration of the two technologies is a non-trivial task due to architectural conflicts between multicasting and DiffServ. We propose an approach for providing multicast support across a DiffServ domain that is scalable in terms of group size, network size, and number of groups. We analyze our approach in a detailed manner for feasibility, adaptiveness, and deployment considerations.
The phenomenal growths of group communications and QoS-aware applications over the Internet have accelerated the development of two key technologies, namely, multicasting and Differentiated Services (DiffServ). Althou...
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ISBN:
(纸本)0769513212
The phenomenal growths of group communications and QoS-aware applications over the Internet have accelerated the development of two key technologies, namely, multicasting and Differentiated Services (DiffServ). Although both are complementary technologies, the integration of the two technologies is a non-trivial task due to architectural conflicts between multicasting and DiffServ. We propose a protocol for member join/leave in a DiffServ network that is scalable in terms of group size, network size, and number of groups. We detail our join/leave protocol for both intra-domain and inter-domain routing as well as the various different types of multicast trees (single source tree, shortest path tree, shared tree, many-to-many tree). Finally, we present simulation studies regarding the performance of our join/leave protocol.
A real-time segmentation scheme for continuous color images is presented in this paper. The proposed scheme consists of two main steps: (1) seed searching and region growing, (2) region-based change detection. A new c...
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ISBN:
(纸本)0780366859
A real-time segmentation scheme for continuous color images is presented in this paper. The proposed scheme consists of two main steps: (1) seed searching and region growing, (2) region-based change detection. A new color representation model, RBG-Ellipse, is proposed. This color model is similar to the HSI representation. However, the transformation between RGB and RGB-Ellipse is linear. Therefore, we are able to take advantage of noise tolerance processing as well as the efficiency in dealing with color difference computation. By using the proposed segmentation scheme, we implemented applications, (1) intelligent networked visual monitoring system and (2) user interface for distance learning to highlight the value of the proposed scheme. Users can view the results through our web site, http://***.
The enhanced Birkhoff-von Neumann decomposition (EBVND) algorithm, a new class-of scheduling algorithms for input queued (IQ) switches, is introduced. Theoretical analysis shows that the performance of EBVND is better...
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ISBN:
(纸本)0780367111
The enhanced Birkhoff-von Neumann decomposition (EBVND) algorithm, a new class-of scheduling algorithms for input queued (IQ) switches, is introduced. Theoretical analysis shows that the performance of EBVND is better than the Birkhoff-von Neumann decomposition algorithm in terms of throughput and cell delay, and can also provide rate and cell delay guarantees. Wave front Birkhoff-von Neumann decomposition (WFBVND) algorithm and its simplified version WFBVND with logN iterations (WFBVND-logN), the special cases of EBVND, are also introduced and evaluated. Simulations show that WFBVND and WFBVND-logN have much lower average cell delay as compared to the Birkhoff-von Neumann decomposition algorithm.
This paper proposes a new medium access control (MAC) protocol, called Request-TDMA/CDMA, for supporting multimedia traffic in wireless networks. In this hybrid protocol, CDMA (code division multiple access) is laid o...
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This paper proposes a new medium access control (MAC) protocol, called Request-TDMA/CDMA, for supporting multimedia traffic in wireless networks. In this hybrid protocol, CDMA (code division multiple access) is laid over TDMA (time division multiple access), where a time frame has two kinds of slots, namely data slots and control slots. The data slots are used to the user to transmit their data while the control slot holds the information for the next frame's slot allocation. Each data slot in a frame can be simultaneously used by multiple users with the help of uniquely assigned codes. Whenever a user needs to transmit a message, he first sends a request message to the central controller and enters the contention process. The controller takes into consideration the time of generation of a call, the bit rate requirement and the message length while reserving slots for the entire length of the message generated. The user then goes into the transmission phase if he is successful in the contention process, and continues to transmit his data till the entire message is sent. Three scheduling algorithms for the allocation of data slots are proposed and their performance are studied for four classes of traffic. We also analyze our protocol using a two-dimensional Markov chain model, and compute the state transition probabilities and derive the average waiting time for a given system load. By simulation experiments we show that our request-TDMA/CDMA protocol is able to effectively combine the orthogonality of both time and code division multiplexing. Further enhancements are also proposed to decrease the waiting time and increase the average channel utilization.
This paper will propose an efficient algorithm that utilizes the signed-digit representation to compute the kth term of a characteristic sequence generated by a linear feedback shift register of order 3 over GF(q). We...
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Bluetooth has been regarded as a promising solution for wireless connection between hand-held devices. In Bluetooth, a message is segmented into short packets to be transmitted over different frequency bands to random...
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We propose the queue length proportional (QLP) assignment algorithm for input queued switches that considers buffer management and scheduling mechanism inclusively to obtain an optimal assignment of both bandwidth and...
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ISBN:
(纸本)0780367111
We propose the queue length proportional (QLP) assignment algorithm for input queued switches that considers buffer management and scheduling mechanism inclusively to obtain an optimal assignment of both bandwidth and buffer space according to the real traffic load. The bandwidth assignment is implemented by considering both bandwidth and backlogged queue lengths, so that it is possible to obtain a high throughput as well as a low cell loss ratio at the same time. QLP is shown to be able to maximize overall throughputs and improve buffer utilization as compared to those which treat buffer management and scheduling as separate functions.
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