Tight Trade-off in Contention Resolution without Collision Detection

Chen, Haimin; Jiang, Yonggang; Zheng, Chaodong

doi:10.1145/3465084.3467920

Cited by 5 publications

(4 citation statements)

References 28 publications

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“…More recently, Bender et al [6] have shown that in the full-sensing model without collision detection (where processors listen to the channel to learn on which steps there are successful sends but are unable to distinguish between silence and collisions) there is a full-sensing protocol which achieves constant throughput even when the message arrival is adversarial rather than random. Chen et al [7] demonstrate a full-sensing protocol that can achieve a decent throughput, even in the presence of jamming. Despite these advances regarding full-sensing protocols, and other protocols assuming more capabilities from processors than acknowledgement-based protocols [23,13], for acknowledgement-based protocols and even for backoff protocols, the most fundamental possible question remains open: do stable protocols exist at all?…”

Section: Introductionmentioning

confidence: 99%

Instability of backoff protocols with arbitrary arrival rates

Goldberg¹,

Lapinskas²

2022

Preprint

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In contention resolution, multiple processors are trying to coordinate to send discrete messages through a shared channel with sharply limited communication. If two processors inadvertently send at the same time, the messages collide and are not transmitted successfully. An important case is acknowledgement-based contention resolution, in which processors cannot listen to the channel at all; all they know is whether or not their own messages have got through. This situation arises frequently in both networking and cloud computing. One particularly important example of an acknowledgement-based contention resolution protocol is binary exponential backoff. Variants of binary exponential backoff are used in both Ethernet and TCP/IP, and both Google Drive and AWS instruct their users to implement it to handle busy periods.In queueing models, where each processor has a queue of messages, stable acknowledgement-based protocols are already known (Håstad et al., SICOMP 1996). In queue-free models, where each processor has a single message but processors arrive randomly, it is widely conjectured that no stable acknowledgement-based protocols exist for any positive arrival rate of processors. Despite exciting recent results for full-sensing protocols which assume greater listening capabilities of the processors (see e.g. Bender et al. STOC 2020 or Chen et al. PODC 2021, this foundational question remains open even for backoff protocols unless the arrival rate of processors is at least 0.42 (Goldberg et al. SICOMP 2004). We prove the conjecture for all backoff protocols outside of a tightly-constrained special case, and set out the remaining technical obstacles to a full proof.

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Section: Introductionmentioning

confidence: 99%

Instability of backoff protocols with arbitrary arrival rates

Goldberg¹,

Lapinskas²

2022

Preprint

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“…With binary exponential backoff, if devices begin the protocol at the same time, it takes Θ( log ) time for all the packets to complete, and the throughput achieved is 1/log [16]. Recent work has shown how to achieve Θ(1) throughput even in an adversarial setting [20,27,28], and Chang, Jin, and Pettie [27] showed how to achieve throughput 1/ − ( ), for any > 0.…”

Section: Introductionmentioning

confidence: 99%

Contention Resolution for Coded Radio Networks

Bender,

Gilbert,

Kuhn

et al. 2022

Preprint

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Randomized backoff protocols, such as exponential backoff, are a powerful tool for managing access to a shared resource, often a wireless communication channel (e.g., [1]). For a wireless device to transmit successfully, it uses a backoff protocol to ensure exclusive access to the channel. Modern radios, however, do not need exclusive access to the channel to communicate; in particular, they have the ability to receive useful information even when more than one device transmits at the same time. These capabilities have now been exploited for many years by systems that rely on interference cancellation, physical layer network coding and analog network coding to improve efficiency. For example, Zigzag decoding [56] demonstrated how a base station can decode messages sent by multiple devices simultaneously.In this paper, we address the following question: Can we design a backoff protocol that is better than exponential backoff when exclusive channel access is not required. We define the Coded Radio Network Model, which generalizes traditional radio network models (e.g., [30]). We then introduce the Decodable Backoff Algorithm, a randomized backoff protocol that achieves an optimal throughput of 1 − (1). (Throughput 1 is optimal, as simultaneous reception does not increase the channel capacity.) The algorithm breaks the constant throughput lower bound for traditional radio networks [47][48][49], showing the power of these new hardware capabilities. CCS CONCEPTS• Theory of computation → Online algorithms; Design and analysis of algorithms; Distributed algorithms; • Networks → Network algorithms.

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“…With binary exponential backoff, if 𝑛 devices begin the protocol at the same time, it takes Θ(𝑛 log 𝑛) time for all the packets to complete, and the throughput achieved is 1/log 𝑛 [16]. Recent work has shown how to achieve Θ(1) throughput even in an adversarial setting [20,27,28], and Chang, Jun, and Pettie [27] showed how to achieve throughput 1/𝑒 − 𝑂 (𝜀), for any 𝜀 > 0.…”

Section: Introductionmentioning

confidence: 99%

“…Backoff has been studied in a wide variety of different models. Many of the above papers have assumed that radios can detect collisions; some work has focused on the case where there is no collision detection [21,28,36,37]. The large majority of these protocols have been randomized, but there has been some consideration of deterministic protocols [37,73,75,77].…”

Section: Introductionmentioning

confidence: 99%

Contention Resolution for Coded Radio Networks

Bender

Gilbert

Kühn

et al. 2022

Proceedings of the 34th ACM Symposium on Parallelism in Algorithms and Architectures

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Randomized backoff protocols, such as exponential backoff, are a powerful tool for managing access to a shared resource, often a wireless communication channel (e.g., [1]). For a wireless device to transmit successfully, it uses a backoff protocol to ensure exclusive access to the channel. Modern radios, however, do not need exclusive access to the channel to communicate; in particular, they have the ability to receive useful information even when more than one device transmits at the same time. These capabilities have now been exploited for many years by systems that rely on interference cancellation, physical layer network coding and analog network coding to improve efficiency. For example, Zigzag decoding [56] demonstrated how a base station can decode messages sent by multiple devices simultaneously.In this paper, we address the following question: Can we design a backoff protocol that is better than exponential backoff when exclusive channel access is not required. We define the Coded Radio Network Model, which generalizes traditional radio network models (e.g., [30]). We then introduce the Decodable Backoff Algorithm, a randomized backoff protocol that achieves an optimal throughput of 1 − 𝑜 (1). (Throughput 1 is optimal, as simultaneous reception does not increase the channel capacity.) The algorithm breaks the constant throughput lower bound for traditional radio networks [47][48][49], showing the power of these new hardware capabilities. CCS CONCEPTS• Theory of computation → Online algorithms; Design and analysis of algorithms; Distributed algorithms; • Networks → Network algorithms.

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Tight Trade-off in Contention Resolution without Collision Detection

Cited by 5 publications

References 28 publications

Instability of backoff protocols with arbitrary arrival rates

Instability of backoff protocols with arbitrary arrival rates

Contention Resolution for Coded Radio Networks

Contention Resolution for Coded Radio Networks

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