Capture models for mobile packet radio networks

Lau, Chiew Tong; Leung, Cyril

doi:10.1109/26.141457

Cited by 173 publications

(56 citation statements)

References 21 publications

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“…In the linearization procedure of Section 3, we only considered the terms corresponding to maximum SINR, which were exactly those cases where none of the interfering nodes were transmitting at the same time as the node under consideration. In contrast, the capture effects are present in Qualnet simulations, which are known to affect throughput performance considerably [51]. Nevertheless, the analytical model seems to capture the general trend and provide a striking correlation, even in a scenario with 100 nodes, where the contention degree and hidden terminals are significant.…”

Section: Model Limitationsmentioning

confidence: 90%

“…In most situations, however, the powers of the received signals are subject to large-scale path loss propagation, shadowing, and small-scale multipath fading [50]. Even when packets from different nodes overlap in time, it may still be possible to successfully decode the packet with the strongest received signal strength-the socalled capture phenomenon [51]. Moreover, a number of choices in system design at the PHY layer have a direct impact on the successful reception of a packet by a given receiver.…”

Section: Impact Of the Phy Layermentioning

confidence: 99%

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A scalable model for channel access protocols in multihop ad hoc networks

Carvalho

Garcia-Luna-Aceves

2004

Proceedings of the 10th Annual International Conference on Mobile Computing and Networking

108

113

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A new modeling framework is introduced for the analytical study of medium access control (MAC) protocols operating in multihop ad hoc networks. The model takes into account the effect of physical-layer parameters on the success of transmissions, the MAC protocol on the likelihood that nodes can access the channnel, and the connectivity of nodes in the network. A key feature of the model is that nodes can be modeled individually, i.e., it allows a per-node setup of many layer-specific parameters. Moreover, no spatial probability distribution or a particular arrangement of nodes is assumed; the model allows the computation of individual (per-node) performance metrics for any given network topology and radio channel model. To show the applicability of the modeling framework, we model multihop ad hoc networks using the IEEE 802.11 distributed coordination function and validate the results from the model with discreteevent simulations in Qualnet. The results show that our model predicts results that are very close to those attained by simulations, and requires seconds to complete compared to several hours of simulation time.

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Section: Model Limitationsmentioning

confidence: 90%

Section: Impact Of the Phy Layermentioning

confidence: 99%

A scalable model for channel access protocols in multihop ad hoc networks

Carvalho

Garcia-Luna-Aceves

2004

Proceedings of the 10th Annual International Conference on Mobile Computing and Networking

108

113

View full text Add to dashboard Cite

show abstract

“…An interrogator can determine the RN16 of the strongest tag and request that it backscatter the . This phenomenon is known as the capture effect and is discussed in [7]. Given the last two conditions, a new efficiency metric to include these effects must be defined.…”

Section: Extending the Optimal Algorithmmentioning

confidence: 99%

“…It can be simplified to yield (13) because . This is definitely greater than from (7). Therefore, the efficiency of reading can be improved over if tags can be read in collided slots (i.e., captured).…”

Section: Extending the Optimal Algorithmmentioning

confidence: 99%

An Optimal Q-Algorithm for the ISO 18000-6C RFID Protocol

Maguire¹,

Pappu²

2009

IEEE Trans. Automat. Sci. Eng.

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Abstract-Passive radio-frequency identification (RFID) systems based on the ISO/IEC 18000-6C (aka EPC Gen2) protocol have typical read rates of up to 1200 unique 96-bit tags per second. This performance is achieved in part through the use of a medium access control algorithm, christened the Q-algorithm, that is a variant of the Slotted Aloha multiuser channel access algorithm. We analyze the medium access control algorithm employed by the ISO/IEC 18000-6C RFID air interface protocol and provide a procedure to achieve optimal read rates. We also show that theoretical performance can be exceeded in many practical use cases and provide a model to incorporate real-world data in read-rate estimation.Note to Practitioners-Estimating read-rates in RFID has always been something of a black art. At one end of the spectrum, in the pure-theory approach, rates are estimated by taking the duration per bit and calculating the total number of bits that can be decoded per second. This approach does not take any of the protocol overheads or real-world conditions into account. In the pure-experimental approach, a standard test case is used to relatively compare read-rates as several factors-tags, readers, firmware, protocols, etc., are varied. Neither of these approaches really provides any insight into the problem of estimating read rates for the general case.In this paper, we take on this problem by developing a first-principles model of collision probability in the Gen2 medium access control layer. Collisions of tag responses are a dominant factor in determining read rates in Gen2 systems. Using this model, we show that the worst case efficiency of the protocol can be no less than 36.8%, i.e., it should be possible to see more than 36.8% of a given population of tags per unit time. We them develop a dynamic Q-algorithm that performs much better than the worst case, and show its performance relative to a static Q-algorithm.We then relax the assumptions underlying the above algorithm so as to be able to incorporate real-world situations and provide a framework wherein practitioners can make some measurements of a particular situation and use our model to estimate expected read rates. Three important factors that need to be considered are: (i) the different decoding times for different types of slot-occupancy; (ii) the capture effect, wherein a two-occupancy slot is decoded as a valid tag because the backscatter powers are sufficiently different; and (iii) the distribution of backscatter powers. We develop a model to account for these three factors.Although our models make several assumptions, we have designed and deployed readers that justify almost all of them. We are currently working on developing a deeper characterization of the backscatter power distribution of a population of tags. This will allow us to use the signal processing capability of our readers to Manuscript received July 29, 2007 disambiguate two-occupancy slots and boost read rates well-above those predicted by our model. This is the focus of our current resear...

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“…It is well known that traditional WLANs are of "point-tomultipoint" architecture, with which each AP serves a number of users in a particular area and each user associates with only one AP, usually the nearest one. Although such an architecture can work well in the networks with sparse user distributions, in high density WLANs it is insufficient to meet the requirement of the resilience of transmission due to the following reasons: 1) Capture effect: The capture effect [19] [20] makes the users far away from their associated AP suffer more backoffs than others, which results in serious unfairness among users in different positions. Especially in the network with high density, the frequent collisions due to capture may starve the users far away from the AP.…”

Section: Introductionmentioning

confidence: 99%

Leveraging multi-AP diversity for transmission resilience in wireless networks: architecture and performance analysis

Zhu

Zhang

Niu

et al. 2009

IEEE Trans. Wireless Commun.

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Abstract-With the increasing development of IEEE 802.11 based Wireless Local Area Network (WLAN) devices, large-scale multi-cell WLANs with a high density of users and access points (APs) have emerged widely in various hotspots. Providing resilient data transmission has been a primary challenge for scaling the WLANs because the high density of users and APs results in too many collisions. In this paper, we analyze and point out the defect of the single association mechanism defined in IEEE 802.11 on transmission reliability from a network perspective. Then, we propose a "multi-AP" architecture with which a MAC layer device called an AP Controller (AC) is employed to enable each user to associate and cooperate with multiple APs. In this way, the users can benefit from the diversity effect of multipaths with independent collisions and transmission errors. This paper concentrates on the theoretical analysis of performance comparison between the proposed "Multi-AP" architecture and that in IEEE 802.11. Extensive simulation results show that the proposed "multi-AP" architecture can obtain much better performance in terms of the throughput per user and the total throughput, and the performance gain is position dependent. Moreover, the unfairness issue in traditional WLANs due to capture effect can be alleviated properly in the "multi-AP" framework.

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Capture models for mobile packet radio networks

Cited by 173 publications

References 21 publications

A scalable model for channel access protocols in multihop ad hoc networks

A scalable model for channel access protocols in multihop ad hoc networks

An Optimal Q-Algorithm for the ISO 18000-6C RFID Protocol

Leveraging multi-AP diversity for transmission resilience in wireless networks: architecture and performance analysis

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