Delay-Bounded Routing for Shadow Registers

The on-chip timing behaviour of synchronous circuits can be quantified at run-time by adding shadow registers, which allow designers to sample the most critical paths of a circuit at a different point in time than the user register would normally. In order to sample these paths precisely, the path skew between the user and the shadow register must be tightly controlled and consistent across all paths that are shadowed. Unlike a custom IC, FPGAs contain prefabricated resources from which composing an arbitrary routing delay is not trivial. This paper presents a method for inserting shadow registers with a minimum skew bound, whilst also reducing the maximum skew. To preserve circuit timing, we apply this to FPGA circuits post place-and-route, using only the spare resources left behind. We find that our techniques can achieve an average STA reported delay bound of ±200ps on a Xilinx device despite incomplete timing information, and achieve <1ps accuracy against our own delay model

Delay-bounded medium access for unidirectional wireless links

Consider a wireless network where links may be unidirectional, that is, a computer node A can broadcast a message and computer node B will receive this message but if B broadcasts then A will not receive it. Assume that messages have deadlines. We propose a medium access control (MAC) protocol which replicates a message in time with carefully selected pauses between replicas, and in this way it guarantees that for every message at least one replica of that message is transmitted without collision. The protocol ensures this with no knowledge of the network topology and it requires neither synchronized clocks nor carrier sensing capabilities. We believe this result is significant because it is the only MAC protocol that offers an upper bound on the message queuing delay for unidirectional links without relying on synchronized clocks

Delay-bounded range queries in DHT-based peer-to-peer systems

2006-2007 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

On the Throughput-Delay Trade-off in Georouting Networks

We study the scaling properties of a georouting scheme in a wireless multi-hop network of $n$ mobile nodes. Our aim is to increase the network capacity quasi linearly with $n$ while keeping the average delay bounded. In our model, mobile nodes move according to an i.i.d. random walk with velocity $v$ and transmit packets to randomly chosen destinations. The average packet delivery delay of our scheme is of order $1/v$ and it achieves the network capacity of order $\frac{n}{\log n\log\log n}$. This shows a practical throughput-delay trade-off, in particular when compared with the seminal result of Gupta and Kumar which shows network capacity of order $\sqrt{n/\log n}$ and negligible delay and the groundbreaking result of Grossglausser and Tse which achieves network capacity of order $n$ but with an average delay of order $\sqrt{n}/v$. We confirm the generality of our analytical results using simulations under various interference models.Comment: This work has been submitted to IEEE INFOCOM 201

Bounded Delay Scheduling with Packet Dependencies

A common situation occurring when dealing with multimedia traffic is having large data frames fragmented into smaller IP packets, and having these packets sent independently through the network. For real-time multimedia traffic, dropping even few packets of a frame may render the entire frame useless. Such traffic is usually modeled as having {\em inter-packet dependencies}. We study the problem of scheduling traffic with such dependencies, where each packet has a deadline by which it should arrive at its destination. Such deadlines are common for real-time multimedia applications, and are derived from stringent delay constraints posed by the application. The figure of merit in such environments is maximizing the system's {\em goodput}, namely, the number of frames successfully delivered. We study online algorithms for the problem of maximizing goodput of delay-bounded traffic with inter-packet dependencies, and use competitive analysis to evaluate their performance. We present competitive algorithms for the problem, as well as matching lower bounds that are tight up to a constant factor. We further present the results of a simulation study which further validates our algorithmic approach and shows that insights arising from our analysis are indeed manifested in practice

Hybrid-ARQ Based Relaying Strategies for Enhancing Reliability in Delay-Bounded Networks

Inspired by several delay-bounded mission-critical applications, this paper investigates chase-combining-based hybrid automatic repeat request (CC-HARQ) protocols to achieve high reliability in delay-constrained applications. A salient feature of our approach is to use the end-to-end delay constraint for computing the total number of ARQs permitted in the network, and then optimally distributing them across the nodes so as to minimize packet-drop-probability (PDP), which is the end-to-end reliability metric of interest. Since the chase-combining strategy combines the received packets across multiple attempts, we observe that the PDP of the network depends on the coherence-time of the intermediate wireless channels. As a result, we address the question of computing optimal allocation of ARQs for CC-HARQ strategies under both slow-fading and fast-fading scenarios. For both the channel conditions, we derive closed-form expressions for the PDP, and then formulate several optimization problems for minimizing the PDP for a given delay-bound. Using extensive theoretical results on the local minima of the optimization problems, we synthesize low-complexity algorithms to obtain near-optimal ARQ distributions. Besides using extensive simulation results to validate our findings, a detailed end-to-end delay analysis is also presented to show that the proposed CC-HARQ strategies outperform already known Type-1 ARQ based strategies in several scenarios.Comment: 33 pages. arXiv admin note: text overlap with arXiv:2203.0838

Implementing ZigBee assisted power management for delay bounded communication on mobile devices

Over the years WiFi has gained immense popularity in networking devices to transfer data over short distances. WiFi communication can consume a lot of energy on battery powered devices like mobile phones. The Standard Power Saving Management(SPSM) which is part of the standard specification for wireless LAN technology has been applied widely. However, it may not deliver satisfactory energy effiiciency in many cases as the wakeup strategy adopted by it cannot adapt dynamically to traffic pattern changes. Motivated by the fact that it has been more and more popular for a mobile device to have both WiFi and other low-power wireless interfaces such as Bluetooth and ZigBee, we propose an implementation of a ZigBee-assisted Power Saving Management (ZPSM) scheme, leveraging the ZigBee interface to wake up WiFi interface based on the delay bound to improve energy efficiency. The results obtained by applying this scheme on a Linux environment shows that ZPSM can save energy significantly without violating delay requirements in various scenarios