The L4S standard has been gaining ground in the recent past, bringing together application and network service providers for building a more responsive internet. While application providers are working towards enabling L4S in their interactive applications, service providers are building dual queue architectures in their access networks. However, the state-of-the-art applies L4S to entire flows and may raise fairness considerations, esp. if there is deliberate abuse of the standard. While queue protection policing is currently also being developed, we propose novel methods for selectively enabling L4S, premised on judicious use of the low latency queue resource. In our proposal, we consider both ultra-low latency and low latency interactive video applications, wherein L4S is invoked based on PES picture size and CMAF chunk/fragment size, respectively. Further, we also contemplate transport layer handling with independent L4S and non-L4S QUIC streams and separate send/receive buffers when both pathways are used in conjunction for delivery. We conclude with recommendations of future work for further evaluation and development of our proposed methods.

Communication among wireless sensor nodes that employ cheap low-power transceivers is often very sensitive to the variations of the wireless channel. Sensor network routing protocols thus strive to continually adapt to temporal variations in wireless links in order to avoid wasteful transmissions over low-quality links. Such adaptive routing protocols must rely on a scheme that can not only accurately estimate the quality of wireless links in terms of a quantitative measure, such as the packet success rate (PSR), but also quickly adapt to temporal dynamics of the links. Traditionally, the PSR is estimated from the fraction of successful transmissions over a window of test- packets. However, we demonstrate that counting based methods do not react to changes in the wireless channel fast enough and that the only way to address this problem is to estimate the PSR based on the receiver's characteristics and on the signal to noise ratio (SNR) at the receiver. We thus propose a scheme that uses a pre-calibrated SNR-PSR relationship and instantaneous SNR estimates to calculate the PSR of the link. In our scheme, each receiver continuously tracks the SNR using a Kalman Filter to minimize the estimation error and uses a locally available SNR- PSR curve to estimate the PSR. Through extensive experiments we demonstrate that our scheme adapts to variations in the channel faster than counting-based PSR estimators and that it also provides better PSR estimates than these counting-based approaches.

This paper introduces a novel cross layer medium access control protocol for multiple beam antennas to fully utilize their multiple-beam-forming capability. Our protocol, explicit synchronization via intelligent feedback (ESIF), uses feedback from neighboring nodes to synchronize data communication at multiple beams. ESIF exploits routing information to guarantee long-term fairness and minimize the energy and latency overheads. Unlike previous works on directional antennas that discuss range extension, we focus on optimal spatial reuse. Simulation results demonstrate that ESIF outperforms other on-demand access schemes based on IEEE 802.11 DCF for multiple beam antennas

Multiple beam antennas can receive (or transmit) data on multiple beams simultaneously. The aim of this paper is to show the limitations of using IEEE 802.11 distributed coordination function (DCF) based schemes for medium access control (MAC) in such antennas. We provide four different variants of IEEE 802.11 DCF based on-demand protocols to study this phenomenon. Our simulation results and analyses emphasize the need to develop a novel MAC protocol to fully exploit the capabilities of multiple beam antennas. We further provide some embryonic guidelines for the development of such a protocol

In our paper, we investigate some MAC layer issues associated with the use of multiple-beam smart antennas at nodes in a distributed wireless ad-hoc network. We propose a transmitter-initiated on-demand MAC protocol that exploits the spatial parallelism in the transmission of packets at a node. We devise two MAC scheduling strategies in the one-hop neighborhood of a node, largest edge first (LEF) and largest degree node first (LDNF), that allow spatial parallelism to be exploited in the transmission as well as reception of packets. Our simulation results indicate that significant gain may be achieved through our scheduling strategies in a one-hop traffic bottleneck.

We consider the medium access control (MAC) protocol design for nodes in a wireless LAN that use a wide-azimuth switched beam smart antenna system comprised of a multiple beam antenna array. The one-hop performance of carrier sense multiple access (CSMA) as well as slotted aloha for such a system is presented analytically and through simulation. The problem of synchronization of multiple beams in CSMA is investigated in our analysis. Our results show that, under heavy offered load conditions, CSMA is a good choice with nodes that have multiple-beam smart antennas, despite the performance loss due to the beam synchronization, providing a stable throughput that approaches unity and is invariant to fluctuations in the offered load. Slotted Aloha, on the other hand, is capable of higher peak throughput in a narrow range of offered loads as more switched beams are employed, but performance drastically reduces beyond optimum offered loads. We also introduce a method, expanded receive rule (ERR), whereby the tight synchronization among different beams of a receiver node in CSMA is relaxed, which is observed to provide better throughput. Finally, we also present performance results for a 4-way-handshake-type carrier sense mechanism using multiple beam antennas.

In wireless sensor networks, a good cost metric encapsulating wireless link quality is essential to an energy-efficient routing topology. For many wireless network scenarios, rapid variation in the channel precludes an efficient mechanism for knowing instantaneous link quality at the time of transmission, thus making it difficult to estimate the instantaneous value of the cost metric. This paper explores what a good cost metric may be and how it can be measured in an energy-efficient way. We present an experimental study of wireless link quality variation over a period of several days in a sensor network placed in two different indoor office environments. The nodes are equipped with low power transceivers operating in the 900 MHz band. Results are documented for several different link configurations, i.e., relative placement of the transmitter and receiver. Based on detailed observations of link quality variation, we form quantitative measures of link quality, and propose a cost metric. We find that reasonably few channel measurements are sufficient to obtain a good estimate of the cost metric, hence even during the initialization phase one can obtain sufficient information about links in order to design an efficient topology. The estimate can be improved further as more measurements are taken during the normal operation of the network.

Recently, MAC protocols using directional antennas for wireless ad hoc networks that are based on and similar to IEEE 802.11 type WLAN have been proposed. These protocols, however, are unable to attain substantial performance improvements because they do not enable the nodes to perform multiple simultaneous transmissions/receptions. In this paper, we propose a MAC layer protocol that exploits space division multiple access, thus using the property of directional reception to receive more than one packet from spatially separated transmitter nodes (equipped with smart antenna systems). Our simulation results show that drastic throughput improvements may be achieved through this scheme.

The use of directional antennas in cellular wireless networks offers many advantages such as range extension, reduced interference for signal detection and improved throughput. MAC protocols using directional antennas for wireless ad hoc networks that are based on and similar to IEEE 802.11 type WLANs have been proposed. We explore 'multiplexing in space' with directional antennas to enhance the total throughput at a bottleneck node in the network. We develop an access protocol for antenna systems that can transmit to multiple destinations simultaneously (and possibly receive from multiple sources as well). Some issues enabling multiple access in space for ad hoc network nodes are discussed. Our simulation results show that the current 802.11 MAC scheme using omnidirectional antennas for channel access fairs very poorly as the bandwidth demand increases. In contrast, we see substantial improvement when spatial multiplexing is employed.