On the Age of Information in a CSMA Environment

Abstract

In this paper, we investigate a network of N interfering links contending for the channel to send their data by employing the well-known Carrier Sense Multiple Access (CSMA) scheme. By leveraging the notion of stochastic hybrid systems, we find a closed form of the total average age of the network in this setting. Armed with this expression, we formulate the optimization problem of minimizing the total average age of the network by calibrating the back-off time of each link. By analyzing its structure, the optimization problem is then converted to an equivalent convex problem that can be solved efficiently to find the optimal back-off time of each link. Insights on the interaction between the links is provided and numerical implementations of our optimized CSMA scheme in an IEEE 802.11 environment is presented to highlight its performance. We also show that, although optimized, the standard CSMA scheme still lacks behind other distributed schemes in terms of average age in some special cases. These results suggest the necessity to find new distributed schemes to further minimize the average age of any general network.

AI-Assisted Low Information Latency Wireless Networking

“…For theoretical optimality, it is shown by [5] that a round-robin scheduling scheme which requires small signaling overhead, is asymptotically optimal with a large number of terminals under certain conditions such as no transmission failures. In [6]- [9], another important aspect regarding the uplink uncoordinated access design is investigated. Unlike scheduled access, terminals have to decide whether to transmit in each time slot autonomously and efficiently.…”

“…Unlike scheduled access, terminals have to decide whether to transmit in each time slot autonomously and efficiently. Optimizations over the transmit probability (i.e., p tx,n where n is the terminal index), or equivalently the contention backoff window size, in CSMA/ALOHA are carried out in [7]- [9], considering terminals may have different channel conditions, service rates and packet arrival rates, respectively; however, the transmission probability is constant over time once decided in these works. In [6], dynamic access probability over time (i.e., p tx,n (t)) according to the terminals' states is proposed, adopting the index approach to prioritize terminals.…”

“…Unlike communication latency, information latency accounts for not only the end-toend latency, but also communication reliability (unsuccessful updates cannot improve the information latency), sensing Scheduling [3] Bernoulli Ideal [4] Buffered sources Physical model [5] Round-robin Bernoulli Ideal [6] Prioritized CSMA ptx,n(t) [7] ALOHA Active sources i.i.d. error ptx,n [8] CSMA and round-robin Bernoulli/Active sources Ideal [9] CSMA Poisson Backoff window [10] General network ALOHA Active/Buffered sources ptx,n [11] Active sources i.i.d. error ptx,n and packet arrival rates latency, information processing latency and all aspects of the information acquisition process that adds to the end effect of information latency.…”

Closed-Form Expression for the Average Age of Information in a Multi-Source M/G/1 Queueing Model

“…Finally, substituting (22) in (20) and (21) results in the expressions (18) and (19), respectively. (17): Let us now focus on the first conditional (17).…”

“…where equality (a) follows from the notations in (22). DRAFT Thus, applying Lemma 4, the conditional expectation in (32) is given as…”