Higher Aggregate Throughput Research Articles

Performance Analysis and Energy Efficiency of MU- (OFDMA & MIMO) Based Hybrid MAC Protocol of IEEE 802.11ax WLANs

Future wireless networks are characterized by densely populated stations (STAs) with limited battery capacity. These networks demand high aggregate throughput, increased energy efficiency, and high Random Access (RA) capability, i.e., the system's ability to allow new STAs to join the network quickly. WiFi-6 (also known as IEEE 802.11 ax) is the new generation WLAN standard proposed to meet these diverse system requirements. In this paper, we analyze the effect of Multi-User Multi-Input Multi-Output (MU-MIMO) & MU-Orthogonal Frequency Division Multiple Access (MU-OFDMA)-based Hybrid Access (HA) mechanism of WiFi-6 systems. We propose a fixed Point model for analyzing this HA mechanism. By solving the system model, we investigate the impact on critical system metrics such as throughput, energy efficiency, Random Access capability, and delay due to a variation in (i) the number of resource units (RUs), (ii) the channel sounding interval, and (iii) the Target Wake-Up time interval. We have studied the effect of the non-saturated traffic model driven by the Poisson and Pareto arrival processes. Further, we have modeled the buffer status-based dynamic scheduling of RUs for the MU-OFDMA-based HA mechanism. We have also analyzed the novel Multi-Traffic Identifier-based frame aggregation feature. Further, we have analyzed the hand-off mechanism for a multi-BSS (Basic Service Set) scenario using the Stochastic geometry-based mathematical tool. We have used Matlab-based simulations for our study and found that the simulation results closely match the analytical results. Our study sheds light on the trade-off that exists between different performance metrics of the 802.11ax HA mechanism.

Multipath Congestion Control: Measurement, Analysis, and Optimization From the Energy Perspective

Multipath TCP (MPTCP) is a promising TCP extension that exploits different Internet paths between a pair of hosts to obtain high aggregate throughput, while it also brings the concern of energy consumption. There has been a lively interest in the design of energy-efficient MPTCP. The research community, however, lacks a comprehensive understanding of which components in an MPTCP congestion control algorithm play the fundamental role in energy efficiency, how various algorithms compare against each other from energy-consuming perspective, or whether there exist potentially better solutions for energy saving. This paper takes the first step towards answering these questions. Through realworld MPTCP Linux kernel experiments, we show that the energy consumption is related to three major aspects: average throughput, path delay and different network scenarios. In order to bridge congestion control to the three aspects, we analyze the existing algorithms and capture the essential parameters of multipath congestion control model related to energy efficiency. Then we propose a window increase factor to shift traffic to low-delay energy-efficient paths. To further extend this design, we apply an energy-aware compensative parameter to fit the general hierarchical Internet topology. Our evaluation indicates that the enhanced congestion control module can successfully improve MPTCP energy efficiency without affecting its transmission performance.

Fast Data Recovery for Improved Mobility Support in Multiradio Dual Connectivity

Data aggregation is one of the crucial features of the 3GPP Multi-Radio Dual Connectivity (MR-DC) technology. However, mobility events and radio link failures, which may occur during the data aggregation, may pose challenges in meeting the latency, reliability, and throughput key performance indicators (KPIs). Unlike single connectivity, the user equipment (UE) in MR-DC operation can experience such events in either of the two base stations (BSs) serving the UE with MR-DC. In typical MR-DC deployments, these events occur more frequently in the BS acting as the secondary node (SN) since the SN operates at a higher frequency band. In this paper, we show that handovers (HOs) and signal blockage events that occur at the SN can create out-of-order data reception or losses at the UE’s Packet Data Control Protocol (PDCP) layer, making the application stop receiving data for up to hundreds of milliseconds. Thus, challenging to meet the KPIs defined for such application. To mitigate this effect, we propose an intelligent and efficient mechanism that operates in the transmitting PDCP layer and significantly minimizes the data interruption periods suffered by the application when the UE aggregates data and HOs or failures of the SN occur. We use LTE/NR testbed experiments to show that the proposed mechanism achieves a high and stable aggregate throughput with near-zero interruption time and data reliability of at least five nines without transport layer retransmissions. The experiments are conducted for saturated TCP traffic and under link quality variations based on traces extracted from a Nokia-proprietary system-level simulator.

Token-Based Adaptive MAC for a Two-Hop Internet-of-Things Enabled MANET

In this paper, a distributed token-based adaptive medium access control (TA-MAC) scheme is proposed for a two-hop Internet of Things (IoT)-enabled mobile ad hoc network. In the TA-MAC, nodes are partitioned into different one-hop node groups, and a time division multiple access (TDMA)-based superframe structure is proposed to allocate different TDMA time durations to different node groups to overcome the hidden terminal problem. A probabilistic token passing scheme is devised to distributedly allocate time slots to nodes in each group for packet transmissions, forming different token rings. The distributed time slot allocation is adaptive to variations of the number of nodes in each token ring due to node movement. To optimize the medium access control (MAC) design, performance analytical models are presented in closed-form functions of both MAC parameters and network traffic load. Then, an average end-to-end delay minimization framework is established to derive the optimal MAC parameters under a certain network load condition. Analytical and simulation results demonstrate that, by adapting the MAC parameters to the varying network condition, the TA-MAC achieves consistently minimal average end-to-end delay, bounded delay for local transmissions, and high aggregate throughput. Further, the performance comparison with other MAC schemes shows the scalability of the proposed MAC in an IoT-based two-hop environment with an increasing number of nodes.

The Performance of Successive Interference Cancellation in Random Wireless Networks

This paper provides a unified framework to study the performance of successive interference cancellation (SIC) in wireless networks with arbitrary fading distribution and powerlaw path loss. An analytical characterization of the performance of SIC is given as a function of different system parameters. The results suggest that the marginal benefit of enabling the receiver to successively decode k users diminishes very fast with k, especially in networks of high dimensions and small path loss exponent. On the other hand, SIC is highly beneficial when the users are clustered around the receiver and/or very low-rate codes are used. In addition, with multiple packet reception, a lower per-user information rate always results in higher aggregate throughput in interference-limited networks. In contrast, there exists a positive optimal per-user rate that maximizes the aggregate throughput in noisy networks. The analytical results serve as useful tools to understand the potential gain of SIC in heterogeneous cellular networks (HCNs). Using these tools, this paper quantifies the gain of SIC on the coverage probability in HCNs with nonaccessible base stations. An interesting observation is that, for contemporary wireless systems (e.g., LTE and WiFi), most of the gain of SIC is achieved by canceling a single interferer.

Picasso

Many applications can benefit from the capability to simultaneously and independently use arbitrarily sized but separate spectrum fragments with a single radio and antenna. By this capability we mean that the radio can simultaneously transmit, simultaneously receive, or simultaneously transmit and receive on arbitrary but separate spectrum fragments. For example, we can use it for spectrum aggregation in fragmented ISM bands as shown in as shown in Fig. 2(A). A WiFi AP can run independent OFDM PHY and CSMA MAC protocols on two WiFi channels to simultaneously serve two legacy WiFi clients assigned to different channels and achieve significantly higher throughput than a legacy AP that is restricted to use only one channel at a time. Similarly, a WiFi client radio with such a capability can use it to simultaneously connect to multiple WiFi APs on different channels and obtain a much higher aggregate throughput than current radios that can transmit or receive on only one channel at a time.

Distributed Scheduling in Multihop Wireless Networks with Maxmin Fairness Provisioning

Fair allocation of resources is an important consideration in the design of wireless networks. In this paper, we consider the setting of multihop wireless networks with multiple routing paths and develop an online flow control and scheduling algorithm for packet admission and link activation that achieves high aggregate throughput while providing different data flows with a fair share of network capacity. For fairness provisioning, we seek to maximize the minimum throughput provided to flows in the network. To cope with different degrees of data reliability among the different links in the network, we use different channel code rates as appropriate. While we expect performance improvement using channel coding and multipath routing, the main contribution of our work is a joint treatment of network stability, multipath routing and link-level reliability in meeting the overarching goal of maxmin fairness. We develop a decentralized, and hence practical, scheduling policy that addresses various concerns and demonstrate, via simulations, that it is competitive with respect to an optimal centralized rate allocator. We also evaluate the fairness provisioning under the proposed algorithm and show that channel coding improves the performance of the network significantly. Finally, we show through simulations that the proposed algorithm outperforms a class of existing approaches on fairness provisioning, which are developed based on utility maximization.

Comparing slotted and continuous CSMA

Carrier-Sense Multiple-Access (CSMA) protocols form a popular class of random-access schemes for regulating node activity in wireless networks. We compare the continuous and the time-slotted versions of this protocol in the saturated regime, and show that continuous CSMA has higher aggregate throughput than the slotted protocol, but this comes at the cost of fairness, i.e., the throughput is not evenly distributed across all nodes. We then release the saturation assumption and consider a multi-hop scenario where packets are forwarded through the network and nodes may occasionally empty. We study end-to-end throughput of both continuous and slotted CSMA, and show that slotted CSMA has a higher throughput than the continuous protocol.

Contrabass

A PHY and MAC protocol for MIMO concurrent transmissions, called Contrabass , is presented. Concurrent transmissions, also referred to as multi-user MIMO, are simultaneous transmissions by multiple interfering nodes over the same carrier frequency. Concurrent transmissions technique has the potential of mitigating the overhead of MAC protocols by amortizing protocol overhead among multiple packets. However, existing proposals for concurrent transmissions could not achieve this as MIMO channel training and collision avoidance typically involve an expensive process of coordination and control message exchanges. This overhead has made MIMO concurrent transmission Impractical and thus unused in real applications. Contrabass implements simultaneous channel training and optimal transmission control without any coordination. As a result, Contrabass achieves very high aggregate throughput, low delays and scalability even under dynamic environments and outperforms the existing MIMO protocols. This is the first practical implementation of MIMO-based concurrent transmissions. We implemented Contrabass in GNU radios and also in NS-2.

SoftRDMA: Implementing iWARP over TCP kernel sockets

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Remote direct memory access (RDMA) allows for the minimization of CPU and memory bus loads associated with network I/O. The Transmission Control Protocol/Internet Protocol (TCP/IP)-based Internet Wide Area RDMA Protocol (iWARP) stack now makes RDMA available for Ethernet local area networks and wide area networks. As 10-Gb/s Ethernet becomes deployed in data centers and Ethernet link speeds continue to increase faster than the memory bus bandwidth, the capability of RDMA to eliminate all intrahost data copy operations related to network I/O makes it attractive for accelerating TCP/IP. Whereas RDMA network adapters offload iWARP/TCP functionality to dedicated hardware, we have designed an onloaded iWARP software implementation, called SoftRDMA, which runs on the host CPU, closely integrated with Linux® TCP kernel sockets. SoftRDMA offers asynchronous nonblocking user-space I/O. It enables iWARP with conventional Ethernet adapters, as well as in mixed iWARP hardware and software environments, facilitating RDMA system integration. Furthermore, SoftRDMA benefits client–server applications with asymmetric loads and high aggregate throughput on the server. With iWARP checksumming turned off, SoftRDMA delivers a throughput exceeding 5 Gb/s using a single CPU core. We suggest zero-copy transmission in software and hardware acceleration for the iWARP framing layer for even higher performance. </para>

Maximizing Communication Concurrency via Link-Layer Packet Salvaging in Mobile Ad Hoc Networks

Carrier-sense medium access control (MAC) protocols such as the IEEE 802.11 distributed coordination function (DCF) avoid collisions by holding up pending transmission requests when a carrier signal is observed above a certain threshold. However, this often results in unnecessarily conservative communication, thus making it difficult to maximize the utilization of the spatial spectral resource. This paper shows that a higher aggregate throughput can be achieved by allowing more concurrent communications and adjusting the communication distance on the fly, which needs provisions for the following two areas. On the one hand, carrier sense-based MAC protocols do not allow aggressive communication attempts when they are within the carrier senseable area. On the other hand, the communication distance is generally neither short nor adjustable because multihop routing protocols strive for providing minimum hop paths. This paper proposes a new MAC algorithm, called multiple access with salvation army (MASA), which adopts less sensitive carrier sensing to promote more concurrent communications and adjusts the communication distance adaptively via packet salvaging at the MAC layer. Extensive simulation based on the ns-2 has shown MASA to outperform the DCF, particularly in terms of delay. We also discuss the implementation of MASA based on the DCF specification

Adaptive peer-to-peer streaming over hybrid wireless networks

In this paper, we propose a centralised Peer-to-Peer (P2P) streaming over hybrid wireless networks to mitigate the congestion at the Access Point (AP) in Wireless Local Area Networks (WLANs). In our proposed architecture, an adaptive receiver-driven mechanism is used to coordinate the streaming from multiple senders. We also propose a peer handoff scheme and an AP handoff scheme for video streaming over hybrid wireless networks. The simulation results show that (1) centralised P2P video streaming over a hybrid wireless network can achieve a much better quality compared to traditional WLAN deployment with heavy background traffic, (2) the adaptive receiver-driven mechanism can synchronise packet delivery from multiple senders, thus increasing streaming quality, (3) the peer handoff scheme enables the receiver to maintain a high aggregate throughput from multiple serving-peers and (4) the AP handoff scheme enables the receiver to roam freely through different cells, while maintaining continuous video streaming.

Operation, system architectures, and physical Layer design considerations of distributed MAC protocols for UWB

Impulse-based ultra wideband (I-UWB) is an attractive radio technology for large ad hoc and sensor networks due to its robustness to harmful multipath effects, sub-centimeter ranging ability, simple hardware, and low radiated power. To scale to large sizes, networks often implement distributed medium access control (MAC) protocols. However, most MAC protocols for I-UWB are centralized, and they target small wireless personal area networks and cellular networks. We propose three distributed MAC protocols suitable for I-UWB. Two multichannel protocols, called multichannel pulse sense multiple access (M-PSMA) and multichannel ALOHA achieve high aggregate throughput. A busy-signal protocol, called busy-signal multiple access (BSMA), reduces the energy wasted from re-transmitted packets. This paper describes the three protocols in terms of the protocol's operation, the supporting system architecture, and the I-UWB physical layer. Physical layer simulations confirm the feasibility of implementing the proposed systems and also provide parameters for network simulations. Network simulations show that the throughput of M-PSMA exceeds that of a centralized time-division multiple-access protocol and that the energy efficiency of BSMA far surpasses that of other distributed protocols.

A flexible MAC protocol for the integration of high- and low-quality video streams, voice and data traffic over high-speed packet switched wireless networks

In this work, we propose and evaluate mechanisms for the multiplexing and the integrated delivery of various traffic types such as video, data and voice, over a wireless cellular high-speed packet switched network. Two different scenarios are examined where the video traffic results from videoconference sessions and high-quality media playback, respectively. In both cases we focus on the uplink channel and we thoroughly investigate, by using actual MPEG-4 video streams, the system's performance under a variety of possible loads. Our goal is to achieve high-aggregate channel throughput while preserving the quality of service requirements of each traffic type.

A Case Study: Energy Efficient High Throughput Chip Multi-Processor Using Reduced-complexity Cores for Transaction Processing Workload

The pursuit of instruction-level parallelism using more transistors produces diminishing returns and also increases power dissipation of general purpose processors. This paper studies a chip multi-processor (CMP) with smaller processor cores as a means to achieve high aggregate throughput and improved energy efficiency. The benefit of this design approach increases as the number of cores on a chip increases, as enabled by semiconductor process scaling. The feasibility of a processor core 40% of the size of a baseline high performance processor that delivers about 70% of its performance is shown. The CMP populated by smaller cores to fill the same silicon area delivers 2.3 times higher performance in transaction processing represented by TPC-C benchmarks than the baseline processor scaled into the same technology. The CMP also achieves 38% higher energy efficiency.

A switched dual antenna array for mobile computing networks

The 2.4GHz licence-free ISM band is used extensively for hosting high performance mobile computing networks. The demand for wireless mobile computing networks with high aggregate throughput and channel quality is countered by the high levels of multipath noise in indoor environments. Although the use of directive antennas has shown good results in overcoming the multipath effect, antennas with large directivity cannot be used in a mobile computing network without affecting the functionality of the wireless protocol used. This paper presents a solution to this problem, introducing a dual antenna diversity scheme for the 2.4GHz ISM band and its beam selector circuit for controlling the diversity scheme. The proposed antenna produces an omnidirectional pattern and two directional patterns with very large nulls in their azimuth pattern, while its low complexity and low cost allows easy integration into consumer products.