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Enabling Multicast Transmission for Spatio-Temporally Asynchronous User Requests in Wireless Environments

Hojung Lee, Jun-Pyo Hong, Wan Choi

TL;DR

The paper tackles the challenge of delivering a file to spatio-temporally asynchronous users in wireless networks without channel state information at the transmitter. It introduces the set-up based merged multicast (SMMC) mechanism, a two-phase approach that aggregates asynchronous requests during a set-up window and then delivers the remaining data via multicast with merged bandwidth, optimizing set-up time and transmission rates to minimize the expected delivery time. By deriving upper and lower bounds on multicast outages and average delivery time, and by solving convex optimization problems for R_UC and R_MC (plus a fine-tuned variant using actual group size), the work provides a principled framework for improving multicast efficiency, with simulations showing meaningful gains over traditional unicast, especially for high-demand data. The methodology enables offline optimization and practical post-set-up tuning, highlighting the potential of SMMC to enhance wireless multicasting in dynamic, CSIT-limited environments.

Abstract

The surge in wireless devices and data traffic volume necessitates more efficient transmission methods. Multicasting has garnered consistent attention as a means to fulfill the increasing demand for more efficient data transmission methods. Nevertheless, leveraging multicast wireless networks for spatio-temporally asynchronous data requests poses challenges. In this context, this paper introduces a new multicast mechanism called \emph{set-up based merged multicast (SMMC)} to minimize the delivery time of the requested file in wireless networks by considering the uncertainties inherent in wireless channels. The proposed mechanism comprises two phases. The first phase involves gathering asynchronous requests for a file from users experiencing diverse channel conditions. During this phase, packets of the requested file are transmitted individually in unicast mode within a specified set-up time. Following this, the second phase initiates multicast transmission, which sequentially handles the remaining packets of the file in multicast mode. In the proposed mechanism, we optimize the set-up time and transmission rates of both unicast and multicast modes to minimize the expected file delivery time by jointly taking into account the statistical characteristics of wireless channels, users' locations, and file popularity. Additionally, we also delve into a \emph{fine-tuned SMMC} by utilizing posterior information on the multicast group size and further improve the performance. Our performance evaluations reveal that the proposed SMMC outperforms conventional unicast methods, especially with high-demand data.

Enabling Multicast Transmission for Spatio-Temporally Asynchronous User Requests in Wireless Environments

TL;DR

The paper tackles the challenge of delivering a file to spatio-temporally asynchronous users in wireless networks without channel state information at the transmitter. It introduces the set-up based merged multicast (SMMC) mechanism, a two-phase approach that aggregates asynchronous requests during a set-up window and then delivers the remaining data via multicast with merged bandwidth, optimizing set-up time and transmission rates to minimize the expected delivery time. By deriving upper and lower bounds on multicast outages and average delivery time, and by solving convex optimization problems for R_UC and R_MC (plus a fine-tuned variant using actual group size), the work provides a principled framework for improving multicast efficiency, with simulations showing meaningful gains over traditional unicast, especially for high-demand data. The methodology enables offline optimization and practical post-set-up tuning, highlighting the potential of SMMC to enhance wireless multicasting in dynamic, CSIT-limited environments.

Abstract

The surge in wireless devices and data traffic volume necessitates more efficient transmission methods. Multicasting has garnered consistent attention as a means to fulfill the increasing demand for more efficient data transmission methods. Nevertheless, leveraging multicast wireless networks for spatio-temporally asynchronous data requests poses challenges. In this context, this paper introduces a new multicast mechanism called \emph{set-up based merged multicast (SMMC)} to minimize the delivery time of the requested file in wireless networks by considering the uncertainties inherent in wireless channels. The proposed mechanism comprises two phases. The first phase involves gathering asynchronous requests for a file from users experiencing diverse channel conditions. During this phase, packets of the requested file are transmitted individually in unicast mode within a specified set-up time. Following this, the second phase initiates multicast transmission, which sequentially handles the remaining packets of the file in multicast mode. In the proposed mechanism, we optimize the set-up time and transmission rates of both unicast and multicast modes to minimize the expected file delivery time by jointly taking into account the statistical characteristics of wireless channels, users' locations, and file popularity. Additionally, we also delve into a \emph{fine-tuned SMMC} by utilizing posterior information on the multicast group size and further improve the performance. Our performance evaluations reveal that the proposed SMMC outperforms conventional unicast methods, especially with high-demand data.
Paper Structure (16 sections, 8 theorems, 51 equations, 6 figures, 2 algorithms)

This paper contains 16 sections, 8 theorems, 51 equations, 6 figures, 2 algorithms.

Table of Contents

  1. Introduction
  2. System Model & SMMC Mechanism
  3. Network and Channel Models
  4. Set-up based Merged Multicast Mechansim
  5. SMMC delivery time Analysis
  6. Problem Formulation
  7. Multicast Outage Probability with Distributed Users
  8. Upper & Lower Bounds for Average Delivery Time
  9. Optimal Transmission Rates $\&$ Set-up time
  10. Optimal transmission rate analysis
  11. Set-up time selection and fine-tuned SMMC
  12. Simulation Results
  13. Conclusion
  14. Proof of Proposition \ref{['proposition3']}
  15. Proof of Proposition \ref{['proposition4']}
  16. ...and 1 more sections

Key Result

Lemma 1

Taylor1998 Let $A_1, A_2 ,...$ be the occurrence times in a Poisson process of rate $\lambda>0$. Conditioned on total number of occurrence time until $t$ as $N(t)=K$, the random variables $A_1, A_2, \ldots A_K$ have the joint probability density function

Figures (6)

  • Figure 1: Illustration of the system model with user requests for same file $f$ from multiple users ($K=3$). BS has the circular coverage region with radius $D_\text{BS}$ and request timeslot for each users ($t_1,t_2$ and $t_3$) are asynchronous.
  • Figure 2: Illustration of the SMMC mechanism with (a) the set-up phase process and (b) the multicast phase process with $K=3$ users.
  • Figure 3: The averaged minimum cached data size in the set-up phase (solid line) and average cached data size of the last requesting user (dotted line) for different transmission rates ($R_\text{UC}$) at $\lambda_f = 0.002$ and $\lambda_f = 0.004$.
  • Figure 4: Comparison of the upper bound (ub), lower bound (lb) and iterative simulation results (sim) of unicast and SMMC average delivery time versus transmission rate ($R_\text{MC}$) when user request frequency is (a) $\lambda_f=0.002$ and (b) $\lambda_f=0.004$ with a given set-up time $t_{\mathrm{set}}=1000$.
  • Figure 5: (a) The analyzed average delivery time and (b) optimized transmission rate ($R_\text{MC}$) versus the set-up time ($t_\text{set}$) for different user request frequencies $\lambda_f=0.001, 0.002, 0.004$.
  • ...and 1 more figures

Theorems & Definitions (8)

  • Lemma 1
  • Proposition 1
  • Proposition 2
  • Proposition 3
  • Proposition 4
  • Proposition 5
  • Lemma 2
  • Lemma 3