WiFi-Direct与LTE协作视频流系统：设计、评估与优化

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"基于WiFi-Direct的LTE协作视频流系统的设计和评估，旨在解决移动在线视频需求增长与高昂流量费用之间的矛盾。通过整合WiFi-Direct和蜂窝网络，该系统在实际设备上实现了小组内的数据交换、视频流合作，并由WiFi-Direct组主设备负责信息协调、数据中继及LTE协作下载调度。研究发现，当组内部分成员通过D2D通道传输数据时，若其他成员连接传统AP，系统效率可提升72%。此外，实测表明，该系统在三终端组内能支持基于DASH的实时视频流传输达到10Mbps。" 本文是一篇研究论文，主要探讨了如何利用WiFi-Direct技术优化LTE网络下的视频流传输。随着移动设备的普及和在线视频内容的丰富，移动在线视频的需求不断攀升，但高昂的流量费用成为阻碍。WiFi-Direct作为一项常见于大多数移动设备的技术，提供了一种可能的解决方案。研究首先指出，尽管WiFi-Direct广泛存在于移动设备中，但针对其在小组数据传输和合作视频流方面的系统性研究尚不足。因此，作者设计并实现了一个创新的系统，这个系统利用WiFi-Direct的组播能力，让组内的Group Owner设备承担信息交换、数据中继和LTE协同下载调度的任务。通过这样的设计，可以更有效地分担蜂窝网络的压力，尤其是在人口密集地区，避免因过多用户同时请求服务而导致的网络拥塞。实验结果显示，当组内部分成员直接通过Device-to-Device (D2D) 链路进行数据传输时，如果其他成员仍通过传统接入点（AP）连接，整个组的效率显著提高，最高可达72%的提升。这一发现对于优化WiFi-Direct组的部署和设计提供了重要参考。此外，研究人员对系统的性能进行了实际测试。在一个包含三台终端的小组环境中，系统成功支持了基于Dynamic Adaptive Streaming over HTTP (DASH) 的实时视频流，传输速率达到了10Mbps，证明了该方案在实际应用中的可行性与高效性。这篇论文不仅提出了一种结合WiFi-Direct和LTE的协作视频流系统，还通过实验证明了其在提高数据传输效率、节省网络资源方面的潜力。这为未来的移动视频流服务和WiFi-Direct技术的进一步优化提供了理论依据和技术方向。

Design and Evaluation of a WiFi-Direct Based LTE

Cooperative Video Streaming System

Qiang Gong

∗

, Yuchun Guo

∗

, Yishuai Chen

∗

, Yong Liu

†

,FengXie

‡

∗

Beijing Jiaotong University, email: {14120061, ychguo, yschen}@bjtu.edu.cn

†

New York University, email: yongliu@nyu.edu

‡

ZTE Inc., email: xie.feng2@zte.com.cn

Abstract—With the prevailing of mobile phones and online

video contents, the demand for mobile online video is increasing.

The desire, however, is held down by the high mobile trafﬁc cost.

To solve this problem, an off-the-shelf solution is WiFi-Direct

(WFD), which is widely available on a majority of mobile devices.

There is, however, no systematic study of WFD-based group data

transfer and cooperative video streaming on real phones. Thus,

we designed and implemented a WFD-based LTE cooperative

video streaming system, in which the WFD GO (Group Owner)

device takes the responsibility of peer information exchange,

data relay, and LTE cooperative downloading scheduling. Based

on the system, we evaluated the performance of WFD-based

group data sharing, including Ping response delay, throughput,

and power efﬁciency. Valuable ﬁndings were obtained. For

instance, we discovered that when a WFD device connects to a

traditional AP (Access Point), even if there is no data transmission

to/from the AP, the Device-to-Device (D2D) throughput would

decrease by at least 72%. Based on these ﬁndings, we provided

recommendations for the design and deployment of WFD based

D2D systems. We ﬁnally demonstrated the feasibility of WFD

based LTE cooperative video streaming using our system. We

showed that, using multiple realistic LTE networks, a 3-device

cooperative system can provide smooth video streaming with

bitrate more than 10Mbps.

Index Terms—WiFi-Direct, Device-to-Device (D2D), LTE Co-

operation, Video Streaming

I. INTRODUCTION

In crowded venues, such as stadiums or music festivals,

mobile networks are still unable to support surging requests for

online videos. Device-to-device (D2D) technique is a potential

solution. D2D can ofﬂoad a majority of downloading trafﬁc

from cellular networks to D2D links between mobile devices.

In an ideal case, when a group of mobile devices request

the same content, only one copy of the content needs to be

downloaded from the cellular network, and then all the mobile

devices can communicate with each other using their D2D

networks to obtain the content. Certainly, such a problem

can also be solved by wireless broadcast, which, however,

is expensive and inconvenient to deploy and manage. Thus,

this paper focuses on cellular trafﬁc ofﬂoading using D2D

technique.

Among all the proposed D2D techniques, WiFi-Direct

(WFD) is the most available one. It is supported by most

of Android mobile devices. For comparison, other D2D tech-

niques are either lack of device or network support (e.g., LTE

D2D) or unfriendly to end users and complex to implement

(e.g., to enable WiFi Ad Hoc mode in an Android device, a

user usually needs root the phone to obtain special privileges

and install patches). Moreover, WiFi channels have no interfer-

ence with cellular network channels. Thus, it has advantages

over cellular based D2D schemes (e.g., LTE D2D), which

have to coordinate the spectrum allocation between the cellular

channel and the D2D channel.

WFD has attracted some attentions in academia and indus-

try, but the performance of WFD-based data transfer between

two devices and in a WFD group has never been systematically

evaluated. For instance, one of the most important feature of

WFD is the multiple access feature, i.e., a device can join

in a WFD group to communicate with other devices, and at

the same time connect to a conventional WiFi AP to access

the Internet. For comparison, in WiFi tethering, if a mobile

phone acts as an AP, it cannot connect to another traditional

WiFi AP to access Internet. Based on this feature, Siris et

al. [1] proposed to use WFD to improve a client’s download

rate by multiple accesses, and Zhang et al. [2] proposed to

use WFD to render a mobile phone’s screen to large display

while downloading data from the Internet by AP. They all,

however, did not evaluate it on real mobile phones, but used

emulations to estimate the performance. For instance, Siris et

al. [1] used two Rasperry Pi devices to simulate the multiple

access scenario.

In this paper, based on currently available commercial WFD

implementation, we design and implement a WFD Group

Owner (GO)-centric LTE cooperative streaming system. In

this system, GO is the one in control of the group in terms

of device joining, leaving, group information maintenance,

and data broadcasting. Every device utilizes its own cellular

network access to complete the assigned downloading tasks.

In this way, the system aggregates the cellular downloading

capacities of all the devices and shares it among all devices,

and thus the trafﬁc cost of each device is decreased. The

system consists of two key components:

1) Group Owner (GO) relay based ﬁle broadcast unit: its

main functionality is to broadcast ﬁle chunks received

from cellular network to all Group Clients (GC)s and

relieve the relay pressure of GO caused by the under-

lying limitation of the WFD technology: all D2D data

transmissions have to be relayed by GO.

2) A pull-based cooperative LTE downloading scheduling

unit: Its functionality is to let GO allocate and manage

downloading tasks of clients.

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