Frank H. P. Fitzek

MPEG-4 and H.263 video traces for network performance evaluation

MPEG-4 and H.263 encoded video is expected to account for a large portion of the traffic in future wireline and wireless networks. However, due to a lack of sufficiently long frame size traces of MPEG-4 and H.263 encoded videos, most network performance evaluations currently use MPEG-1 encodings. We present and study a publicly available library of frame size traces of long MPEG-4 and H.263 encoded videos, which we have generated at the Technical University Berlin. The frame size traces have been generated from MPEG-4 and H.263 encodings of over 10 video sequences each 60 minutes long. We conduct a thorough statistical analysis of the traces.

Cooperation in Wireless Networks: Principles and Applications

Cooperation in Wireless Networks: Principles and Applications covers the underlying principles of cooperative techniques as well as several applications demonstrating the use of such techniques in practical systems. The work is written in a collaborative manner by several authors from Asia, America, and Europe. Twenty chapters introduce and discuss in detail the main cooperative strategies for the whole communication protocol stack from the application layer down to the physical layer. Furthermore power saving strategies, security, hardware realization, and user scenarios for cooperative communication systems are introduced and discussed. The book also summarizes the strength of cooperation for upcoming generation of wireless communication systems, clearly motivating the use of cooperative techniques and pointing out that cooperation will become one of the key technologies enabling 4G and beyond. This book puts into one volume a comprehensive and technically rich view of the wireless communications scene from a cooperation point of view.

Network Coding for Mobile Devices - Systematic Binary Random Rateless Codes

In this work we consider the implementation of Random Linear Network Coding (RLNC) on battery constrained mobile devices with low computational capabilities such as; sensors, mobile phones and Personal Digital Assistants (PDAs). It is non-trivial to create an efficient implementation of RLNC which is needed to ensure high throughput, low computational requirements and energy consumption. As a consequence there does not, to the best of our knowledge, exist any such implemen- tation for mobile device that allow for throughput close to what can be achieved in e.g. Wireless Local Area Network (WLAN). In this paper we propose to base RLNC on the binary Galois field and to use a systematic code. We have implemented this approach in C++ and Symbian C++ and achieve synthetic encoding/decoding throughput of up to 40/30 MB/s on a Nokia N95-8GB mobile phone and 1.5/1.0 GB/s on a high end laptop. Index Terms—Mobile devices, Network coding, Reliable Mul- ticast. I. INTRODUCTION A large body of existing literature (1) treats the theoretical benefits of Network Coding (NC). However, the costs of implementing NC in terms computational overhead, memory consumption or network usage is often not considered. In this work we consider the implementation of RLNC on mobile bat- tery constrained devices with low computational capabilities, such as sensors, mobile phones or PDAs. The computations performed using RLNC is based on finite fields arithmetic also known as Galois fields. From a coding perspective the field size, q, used should be large to ensure that coded packets are linearly independent, additionally increasing the size of the field elements is advantageous as this reduces the number of

Cellular Controlled Short-Range Communication for Cooperative P2P Networking

This article advocates a novel communication architecture and associated collaborative framework for future wireless communication systems. In contrast to the dominating cellular architecture and the upcoming peer-to-peer architecture, the new approach envisions a cellular controlled short-range communication network among cooperating mobile and wireless devices. The role of the mobile device will change, from being an agnostic entity in respect to the surrounding world to a cognitive device. This cognitive device is capable of being aware of the neighboring devices as well as on the possibility to establish cooperation with them. The novel architecture together with several possible cooperative strategies will bring clear benefits for the network and service providers, mobile device manufacturers and also end users.

Kodo: an open and research oriented network coding library

This paper introduces theKodo network coding library. Kodo is an open source C++ library intended to be used in practical studies of network coding algorithms. The target users for the library are researchers working with or interested in network coding. To provide a research friendly library Kodo provides a number of algorithms and building blocks, with which new and experimental algorithms can be implemented and tested. In this paper we introduce potential users to the goals, the structure, and the use of the library. To demonstrate the use of the library we provide a number of simple programming examples. It is our hope that network coding practitioners will use Kodo as a starting point, and in time contribute by improving and extending the functionality of Kodo.

A prefetching protocol for continuous media streaming in wireless environments

Streaming of continuous media over wireless links is a notoriously difficult problem. This is due to the stringent quality of service (QoS) requirements of continuous media and the unreliability of wireless links. We develop a streaming protocol for the real-time delivery of prerecorded continuous media from (to) a central base station to (from) multiple wireless clients within a wireless cell. Our protocol prefetches parts of the ongoing continuous media streams into prefetch buffers in the clients (base station). Our protocol prefetches according to a join-the-shortest-queue (JSQ) policy. By exploiting rate adaptation techniques of wireless data packet protocols, the JSQ policy dynamically allocates more transmission capacity to streams with small prefetched reserves. Our protocol uses channel probing to handle the location-dependent, time-varying, and bursty errors of wireless links. We evaluate our prefetching protocol through extensive simulations with VBR MPEG and H.263 encoded video traces. Our simulations indicate that for bursty VBR video with an average rate of 64 kb/s and typical wireless communication conditions our prefetching protocol achieves client starvation probabilities on the order of 10/sup -4/ and a bandwidth efficiency of 90% with prefetch buffers of 128 kbytes.

Providing application-level QoS in 3G/4G wireless systems: a comprehensive framework based on multirate CDMA

The emerging applications for 3G and 4G wireless systems typically require highly heterogeneous and time-varying quality of service from the underlying protocol layers. The wireless links, however, provide only an unreliable communication channel that suffers from temporal outages. As a consequence, protocol mechanisms are needed that, based on the unreliable wireless links, provide the different service qualities required by the emerging applications. We identify the emerging IP-based applications for 3G and 4G wireless systems and categorize their QoS requirements. We discuss the wireless access mechanisms that show promise as the basis for supporting these applications. We then propose a set of protocol mechanisms that, based on the discussed wireless access mechanisms, provide the required QoS for the different application categories.

Design and performance of an enhanced IEEE 802.11 MAC protocol for multihop coverage extension

Ad hoc communication is gaining popularity, not only for pure ad hoc communication networks but also as a viable solution for coverage extension in wireless networks. Especially for upcoming WLAN hotspots, this is an interesting option to decrease installation costs. In this article we introduce a new MAC protocol that needs only marginal changes to the standard and enables efficient multihop networking. We advocate the use of multiple IEEE 802.11 channels, where one channel is reserved as a common signalling channel for the task of assigning the others (data channels) among wireless terminals. The proposed MAC protocols are based on a four-way handshake over the common signalling channel, while data transmission occurs on a dedicated channel. We propose a further optimization applying multiple wireless network interface cards. This improvement in performance comes at the price of a slightly more complex hardware. Two different simulation models are implemented to investigate our approach. The first model investigates the MAC protocol and its improvements, while the second model analyzes the multihop performance in terms of delivery ratio and transmission delay. BY means of numerous simulations we present the performance of our MAC approach in comparison with two standard approaches in terms of bandwidth, packet delivery, and transmission delay. For our performance evaluation we apply the IEEE 802.11a technology, but we note that our approach can also be used for IEEE 802.11b.

Implementation and Performance Evaluation of Network Coding for Cooperative Mobile Devices

In this work a performance evaluation of network coding for cooperative wireless networks is carried out. Implementing network coding on commercially available mobile devices, the performance is presented in terms of throughput, delay and energy consumption. In contrast to purely cellular systems, where the mobile devices are only connected to the base station, in cooperative wireless networks, the mobile device, in addition to the cellular communication, establishes short range links to neighboring mobile devices within its proximity. In prior work it has been shown that the newly formed cooperative cluster, also referred as wireless grid, can offer each participating mobile device a better performance in terms of data rate, delay, robustness, security, and energy consumption in contrast to any stand alone device. To improve the performance within the cooperative cluster even more, network coding seems to be a promising technology as it decreases the number of packets to be interchanged among cooperative mobile devices leading to a decreased packet delay. The energy saved by fewer packet transmissions is confronted with the energy needed to carry out the network coding and related overhead. The findings of this paper show that network coding is always beneficial in terms of throughput and delay for the cooperative cluster.

Novel concepts for device-to-device communication using network coding

Device-to-device communication is currently a hot research topic within 3GPP. Even though D2D communication has been part of previous ad hoc, meshed and sensor networks proposals, the main contribution by 3GPP is that the direct communication among two devices is carried out over a dynamically assigned, licensed spectrum; thus, it is under full control of the cellular network. D2D communication creates a market potential for new services, new approaches to efficient spectrum use, and security concepts. This is especially true if D2D communication is extended to larger communication groups organized in meshed clusters. In this article, we discuss the potential and shortcomings of D2D communication as proposed today, advocating for the use of network coding as an enabling technology for enhanced security and communication efficiency using the PlayNCool and CORE protocols as key examples to deliver smarter D2D systems.