PPR: Partial Packet Recovery for Wireless Networks

Bit errors occur over wireless channels when the signal isn't strongenough to overcome the effects of interference and noise. Currentwireless protocols may use forward error correction (FEC) to correct forsome (small) number of bit errors, but generally retransmit the wholepacket if the FEC is insufficient. We observe that current wirelessmesh network protocols retransmit a number of packets and that most ofthese retransmissions end up sending bits that have already beenreceived multiple times, wasting network capacity. To overcome thisinefficiency, we develop, implement, and evaluate a partial packetrecovery (PPR) system.PPR incorporates three new ideas: (1) SoftPHY, an expandedphysical layer (PHY) interface to provide hints to the higher layersabout how ``close'' the actual received symbol was to the one decoded,(2) a postamble scheme to recover data even when a packet'spreamble is corrupted and not decodable at the receiver, and (3) PP-ARQ, an asynchronous link-layer retransmission protocol that allowsa receiver to compactly encode and request for retransmission only thoseportions of a packet that are likely in error.Our experimental results from a 27-node 802.15.4 testbed that includesTelos motes with 2.4 GHz Chipcon radios and GNU Radio nodes implementingthe Zigbee standard (802.15.4) show that PPR increases the framedelivery rate by a factor of 2x under moderate load, and7x under heavy load when many links have marginal quality

A conceptual model of consumer attitudes towards SMS advertising

This paper presents the theoretical applications relevant to a study on the drivers of consumer acceptance of SMS advertising. This paper applies common underlying theories such as the Technology Acceptance Model and Diffusion of Innovation Theory to the field of SMS advertising. Common marketing concepts and theories are also applied to each of the proposed constructs within the study, Utility, Context, Sacrifice, Control, Trust and Attitudes to Advertising in General. This paper then summarises the study in the form of a conceptual framework, presenting a model and proposed hypotheses to be tested

SMS advertising - a critical review and future directions

The area of SMS advertising is relatively new and under-researched within marketing literature. SMS advertising itself is encompassed by the broader areas of M-Commerce and Mobile advertising, which are experiencing rapid growth. A review of literature surrounding the topic of SMS advertising has revealed the key drivers of consumer acceptance. While the broad drivers of acceptance are agreed upon in the literature, researchers disagree on the importance of each issue. This review also presents a summary of the key gaps within SMS advertising literature

Partial OFDM Symbol Recovery to Improve Interfering Wireless Networks Operation in Collision Environments

The uplink data rate region for interfering transmissions in wireless networks has been characterised and proven, yet its underlying model assumes a complete temporal overlap. Practical unplanned networks, however, adopt packetized transmissions and eschew tight inter-network coordination, resulting in packet collisions that often partially overlap, but rarely ever completely overlap. In this work, we report a new design called (), that specifically targets the parts of data symbols that experience no interference during a packet collision. bootstraps a successive interference cancellation (SIC) like decoder from these strong signals, thus improving performance over techniques oblivious to such partial packet overlaps. We have implemented on the WARP software-defined radio platform and in trace-based simulation. Our performance evaluation presents experimental results from this implementation operating in a 12node software network testbed, spread over two rooms in a nonlineofsight indoor office environment. Experimental results confirm that our proposal decoder is capable of decoding up to 60 % of collided frames depending on the type of data and modulation used. This consistently leads to throughput enhancement over conventional WiFi under different scenarios and for the various data types tested, namely downlink bulk TCP, downlink videoondemand, and uplink UDP

PBE-CC: Congestion Control via Endpoint-Centric, Physical-Layer Bandwidth Measurements

Wireless networks are becoming ever more sophisticated and overcrowded, imposing the most delay, jitter, and throughput damage to end-to-end network flows in today's internet. We therefore argue for fine-grained mobile endpoint-based wireless measurements to inform a precise congestion control algorithm through a well-defined API to the mobile's wireless physical layer. Our proposed congestion control algorithm is based on Physical-Layer Bandwidth measurements taken at the Endpoint (PBE-CC), and captures the latest 5G New Radio innovations that increase wireless capacity, yet create abrupt rises and falls in available wireless capacity that the PBE-CC sender can react to precisely and very rapidly. We implement a proof-of-concept prototype of the PBE measurement module on software-defined radios and the PBE sender and receiver in C. An extensive performance evaluation compares PBE-CC head to head against the leading cellular-aware and wireless-oblivious congestion control protocols proposed in the research community and in deployment, in mobile and static mobile scenarios, and over busy and quiet networks. Results show 6.3% higher average throughput than BBR, while simultaneously reducing 95th percentile delay by 1.8x

The SoftPHY Abstraction: from Packets to Symbols in Wireless Network Design

At ever-increasing rates, we are using wireless systems to communicatewith others and retrieve content of interest to us. Current wirelesstechnologies such as WiFi or Zigbee use forward error correction todrive bit error rates down when there are few interferingtransmissions. However, as more of us use wireless networks toretrieve increasingly rich content, interference increases inunpredictable ways. This results in errored bits, degradedthroughput, and eventually, an unusable network. We observe that thisis the result of higher layers working at the packet granularity,whereas they would benefit from a shift in perspective from wholepackets to individual symbols.From real-world experiments on a 31-node testbed of Zigbee andsoftware-defined radios, we find that often, not all of the bitsin corrupted packets share fate. Thus, today's wireless protocolsretransmit packets where only a small number of the constituent bitsin a packet are in error, wasting network resources. In thisdissertation, we will describe a physical layer that passesinformation about its confidence in each decoded symbol up to higherlayers. These SoftPHY hints have many applications, one ofwhich, more efficient link-layer retransmissions, we will describe indetail. PP-ARQ is a link-layer reliable retransmission protocolthat allows a receiver to compactly encode a request forretransmission of only the bits in a packet that are likely in error.Our experimental results show that PP-ARQ increases aggregate networkthroughput by a factor of approximately 2x under variousconditions. Finally, we will place our contributions in the contextof related work and discuss other uses of SoftPHY throughout thewireless networking stack

Consumer acceptance and response to SMS advertising

The rising market penetration of the mobile phone and rapid increase in wireless technology represent significant opportunities for advertisers to reach consumers. Mobile phone advertising has emerged as one of the fastest growing advertising mediums in recent times, and this rise is being led by Short Message Service (SMS) advertising. Despite the growing number of worldwide companies adopting SMS advertising, very little is understood about consumer reactions to this medium. In particular, little academic research has been conducted on consumers’ acceptance of this medium and their behavioural responses to advertising messages. In addition, researchers have thus far been unable to identify the impact of culture on acceptance and response to SMS advertising. This research aims to bridge the gap between academic knowledge and advertising practice by testing five potential drivers of consumer acceptance of SMS advertising as well as the relationships between the acceptance of SMS advertising, intention to receive SMS advertising and behavioural responses to SMS advertising. This research is conducted cross-nationally by comparing Australian and South Korean consumers.In order to test the hypotheses proposed in this study, a survey instrument was developed. This instrument consists of existing scales in the literature as well as a scale developed for the purpose of this study, which measures consumers’ behavioural responses to SMS advertising. Data were collected from 203 Australian and 207 South Korean consumers, from personal and online survey distribution at universities in Australia and South Korea. A series of regression analyses were conducted to test the relationships between the variables, with results compared across samples. The results from this study generally suggest that acceptance, intentions and responses to SMS advertising are similar for Australians and South Koreans. Consumers from the two samples agreed on the importance of four out of the five potential drivers of the acceptance of SMS advertising. The utility of SMS advertisements, context of SMS advertisements and attitudes to advertising in general were found to have a significant impact on the acceptance of either sample. Furthermore, trust in advertisers and laws was important to South Koreans but not to Australians. These results indicate that Australian and South Korean consumers are typically not accepting of SMS advertising, unwilling to receive advertisements and respond negatively to them, while the relationships between these variables are generally strong and consistent.The results from this study highlight the need for advertisers to design SMS advertisements carefully, containing information that is useful, contextually relevant and correctly targeted. In addition, marketers should focus on building relationships with customers and offer incentives to accept SMS advertising in order to improve negative behavioural responses. This study provides useful theoretical contributions to the field of SMS advertising, with an insight into the crosscultural impact of SMS advertising, the development of a new scale to measure behavioural responses to SMS advertising and the application of key marketing theories

Implementation of a power-saving protocol for ad hoc wireless networks

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 58-61).We describe the design and implementation of a power-saving protocol for ad hoc wireless networks. We present the Span power-saving protocol and discuss its implementation in the context of the Linux operating system. We address the issues of ad hoc routing, link layer design, and integration with the Linux networking stack using the 802.11b wireless link technology. From this thesis, we conclude that Span can be implemented on an 802.11b network with reasonable performance for most networking applications. Furthermore, our implementation of Span yields a lifetime improvement of between 12% and 29% at-each node in an ad hoc network. We argue that with additional hardware, Span can outperform conventional 802.11 ad hoc networks in terms of capacity, latency, and power savings.by Kyle Jamieson.M.Eng

Cross-layer wireless bit rate adaptation

This paper presents SoftRate, a wireless bit rate adaptation protocol that is responsive to rapidly varying channel conditions. Unlike previous work that uses either frame receptions or signal-to-noise ratio (SNR) estimates to select bit rates, SoftRate uses confidence information calculated by the physical layer and exported to higher layers via the SoftPHY interface to estimate the prevailing channel bit error rate (BER). Senders use this BER estimate, calculated over each received packet (even when the packet has no bit errors), to pick good bit rates. SoftRate's novel BER computation works across different wireless environments and hardware without requiring any retraining. SoftRate also uses abrupt changes in the BER estimate to identify interference, enabling it to reduce the bit rate only in response to channel errors caused by attenuation or fading. Our experiments conducted using a software radio prototype show that SoftRate achieves 2X higher throughput than popular frame-level protocols such as SampleRate and RRAA. It also achieves 20% more throughput than an SNR-based protocol trained on the operating environment, and up to 4X higher throughput than an untrained SNR-based protocol. The throughput gains using SoftRate stem from its ability to react to channel variations within a single packet-time and its robustness to collision losses.National Science Foundation (U.S.) (Grant CNS-0721702)National Science Foundation (U.S.) (Grant CNS-0520032)Foxconn International Holdings Ltd