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...h of the modulation schemes shown in Figure 1. For the sake of this illustration only large-scale path loss was modeled (in comparison to the rest of our results, in which we modeled Rayleigh fading) =-=[20]-=-. Notice that the lower rate schemes have greater transmission ranges than the higher rate schemes. As the distance increases, the signal attenuates until the received SNR drops below the threshold re...

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...o as soon as the RSH has been received. 5. SIMULATION ENVIRONMENT The results in this paper were generated using the ns-2 network simulator from LBNL [7], with extensions from the CMU Monarch project =-=[5]-=- for modeling mobile ad hoc networks. Included in the simulation are models for a number of trac generators, as well as networking stacks incorporating common ad hoc routing, MAC, and physical layer p...

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... that although our discussion is in the context of the RTS/CTS protocol in the DCF of the 802.11 standard, the concepts are equally applicable to other RTS/CTS based protocols such as SRMA [21], MACA =-=[16-=-], MACAW [4], and FAMA [8]. In RBAR, instead of carrying the duration of the reservation, the packets carry the modulation rate and size of the data packet. This modication serves the dual purpose of ...

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...AutoRate (RBAR) protocol. The novelty of RBAR is that its rate adaptation mechanism is in the receiver instead of in the sender. This is in contrast to existing schemes in devices like the WaveLAN II =-=[15]-=-. We show that RBAR is better because it results in a more ecient channel quality estimation which is then re ected in a higher overall throughput Our protocol is based on the RTS/CTS mechanism and co...

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...m throughput for the given channel conditions. A proven technique for wireline modems [6], rate adaptation has attracted attention as a technique for use in wireless systems as well (e.g., [18], [3], =-=[11]-=-, [24], [2]). In fact, the Lucent WaveLAN II and Aironet PC4800 devices also contain proprietary rate adaptation mechanisms. There are two aspects to rate adaptation: channel quality estimation and ra...

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... the optimum throughput for the given channel conditions. A proven technique for wireline modems [6], rate adaptation has attracted attention as a technique for use in wireless systems as well (e.g., =-=[18]-=-, [3], [11], [24], [2]). In fact, the Lucent WaveLAN II and Aironet PC4800 devices also contain proprietary rate adaptation mechanisms. There are two aspects to rate adaptation: channel quality estima...

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...hanging settings in control packets, such as those in the RTS/CTS protocol. The RTS/CTS protocol is a common MAC protocol for wireless local area networks (e.g., SRMA [21], MACA [16], MACAW [4], FAMA =-=[8]-=-, IEEE 802.11 [12]). The purpose of the protocol is twofold: 1) to coordinate the transfer of the data packet between the sender and receiver, and 2) to announce the duration of the packet transfer to...

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...ughput for the given channel conditions. A proven technique for wireline modems [6], rate adaptation has attracted attention as a technique for use in wireless systems as well (e.g., [18], [3], [11], =-=[24]-=-, [2]). In fact, the Lucent WaveLAN II and Aironet PC4800 devices also contain proprietary rate adaptation mechanisms. There are two aspects to rate adaptation: channel quality estimation and rate sel...

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...of channel quality (e.g., signal-to-noise ratio, signal strength, symbol error rate, bit error rate), which predictors should be used, whether predictions should be short-term or long-term, etc. [3], =-=[10]-=-. Rate selection involves using the channel quality predictions to select an appropriate rate. Techniques vary, but a common technique is threshold selection, where the value of an indicator is compar...

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...ptimum throughput for the given channel conditions. A proven technique for wireline modems [6], rate adaptation has attracted attention as a technique for use in wireless systems as well (e.g., [18], =-=[3]-=-, [11], [24], [2]). In fact, the Lucent WaveLAN II and Aironet PC4800 devices also contain proprietary rate adaptation mechanisms. There are two aspects to rate adaptation: channel quality estimation ...

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...ate rate. Techniques vary, but a common technique is threshold selection, where the value of an indicator is compared against a list of threshold values representing boundaries between the data rates =-=[22-=-], [3]. Among the factors that in uence the eectiveness of rate adaptation, of particular importance is the accuracy of the channel quality estimates. Clearly, inaccurate estimates will result in poor...

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... techniques have been designed for wireless local area networks (e.g., mobile nodes communicating peer-to-peer over CSMA/CA links). Among those that are available, the following are most relevant. In =-=[19]-=-, the authors present a protocol for a dual-channel slotted-aloha MAC, in which a separate control channel is used by the receiver to transmit explicit feedback to the sender, which the sender uses to...

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... for the given channel conditions. A proven technique for wireline modems [6], rate adaptation has attracted attention as a technique for use in wireless systems as well (e.g., [18], [3], [11], [24], =-=[2]-=-). In fact, the Lucent WaveLAN II and Aironet PC4800 devices also contain proprietary rate adaptation mechanisms. There are two aspects to rate adaptation: channel quality estimation and rate selectio...

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...1 and 572Kbps for Flow 2, and in Scenario 2 it was 278Kbps for Flow 1 and 867Kbps for Flow 2. The dierence in the throughputs between thesows in Scenario 2 is due to problems with fairness in 802.11 [=-=23]-=-. For Scenario 1, there is only a moderate impact on performance. At 5% loss there is only a 3% decrease in performance, and the decline stays below 10% beyond a loss of 15%. However, in Scenario 2 we...

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...n algorithm, we used a sample of the instantaneous received signal strength at the end of the RTS reception. In practice, of course, much more accurate techniques could be used, such as those in [3], =-=[17]-=-, and [10]. For the rate selection algorithm, we used a simple threshold based technique. Threshold based techniques have been widely studied (e.g. [22], [3], [11]). In a threshold scheme, the rate is...

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...he best rate based on information from previous data packet transmissions, incrementally increasing or decreasing the rate after a number of consecutive successes or losses, respectively. Finally, in =-=[9]-=-, the authors propose protocol for point-to-point links, that selects transmission settings (e.g. code rate and power level) based on cached per-link information. The settings are stored in separate t...

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...g wireless local area networking devices are designed with the capability of transmitting at multiple data rates. Examples of such devices include WaveLAN II from Lucent [15], and PC4800 from Aironet =-=[1]-=-. 1.1 Rate Adaptation Rate adaptation is the process of dynamically switching data rates to match the channel conditions, with the goal of selecting the rate that will give the optimum throughput for ...

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...witching data rates to match the channel conditions, with the goal of selecting the rate that will give the optimum throughput for the given channel conditions. A proven technique for wireline modems =-=[6]-=-, rate adaptation has attracted attention as a technique for use in wireless systems as well (e.g., [18], [3], [11], [24], [2]). In fact, the Lucent WaveLAN II and Aironet PC4800 devices also contain ...