Jarno Pinola

An experimental investigation of VoIP and video streaming over fixed WiMAX

Despite the significant interest in WiMAX technology and deployment, there are very few publicly reported measurements from testbeds and field trials. As such, most WiMAX studies employ simulation and modeling. This paper contributes to our understanding of what is realistically possible using off-the-shelf fixed WiMAX equipment today. We employ multiple competing traffic sources over a point-to-multipoint WiMAX topology and measure the capacity of the WiMAX equipment to handle a multitude of VoIP flows between subscriber stations while delivering a variable number of video streams. We measure throughput, packet loss, and one-way delay for both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. For the one-way delay measurements we synchronize the clocks of all testbed hosts with a software-only, open source implementation of the IEEE 1588 Precision Time Protocol. We compare these one-way delay measurements with those obtained when GPS-based synchronization is used.

Performance of IEEE 802.11 based WLAN devices under various jamming signals

IEEE 802.11 based WLAN systems have gained interest to be used in the military and public authority environments, where the radio conditions can be harsh due to intentional jamming. The radio environment can be difficult also in commercial and civilian deployments since the unlicensed frequency bands are crowded. To study these problems, we built a test bed with a controlled signal path to measure the effects of different interfering signals to WLAN communications. We use continuous wideband noise jamming as the point of comparison, and focus on studying the effect of pulsed jamming and frequency sweep jamming. In addition, we consider also medium access control (MAC) interference. Based on the results, WLAN systems do not seem to be sensitive to the tested short noise jamming pulses. Under longer pulses, the effects are seen, and long data frames are more vulnerable to jamming than short ones. In fact, even a small amount of long frames in a data stream can ruin the performance of the whole link. Under frequency sweep jamming, slow sweeps with narrowband jamming signals can be quite harmful to WLAN communications. The results of MAC jamming show significant variation in performance between the different devices: The clear channel assessment (CCA) mechanism of some devices can be jammed very easily by using WLAN-like jamming signals. As a side product, the study also revealed some countermeasures against jamming.

ROHC and aggregated VoIP over fixed WiMAX: An empirical evaluation

WiMAX has been at the center of attention in wireless communications during the last years. Nonetheless, very few testbed or field trial measurement accounts have been reported in the peer-reviewed literature. We fill this gap by exploring scenarios where fixed WiMAX is employed for VoIP traffic. VoIP packets typically exhibit large header overheads and small total packet sizes. The actual codec payload per packet is very small compared to the total length of headers appended to each voice frame. Robust header compression (ROHC) can significantly decrease header size by capitalizing on static or rarely changing header fields. Aggregating multiple voice frames into one packet is another attractive and effective way to increase application goodput and overall bandwidth utilization. We study the effect of ROHC and application layer aggregation on VoIP performance in a fixed WiMAX testbed consisting of one base station and two subscriber stations. We find that ROHC increases the number of simultaneous bidirectional emulated VoIP flows by 6% when compared to plain VoIP. When aggregation and ROHC are employed in unison, they allow for 86% more flows than standard VoIP to be sustained in our testbed.

On the Performance Gains of VoIP Aggregation and ROHC over a WirelessMAN-OFDMA Air Interface

A growing number of mobile WiMAX deployments are in progress world-wide and the technology is anticipated to play a key role in next generation mobile broadband wireless networks. However, although the theoretical potential of WiMAX technologies is already well established, independent, publicly released, thorough evaluations of WiMAX network performance in the real world are yet to become available. In this study, we consider synthetic Voice over IP (VoIP) performance over the WirelessMAN-OFDMA air interface of a state of the art mobile WiMAX testbed operating at the 3.5 GHz frequency band and quantify the benefits of employing VoIP aggregation and Robust Header Compression (ROHC). Although VoIP aggregation and ROHC have been proposed and thoroughly evaluated through simulation and modeling, this is the first study to present empirical results from employing them over the Wireless MANOFDMA air interface of a real-world WiMAX system. Our results indicate that the combined use of VoIP aggregation and ROHC can increase the number of flows sustained without loss by approximately a factor of three.

A measurement study of Speex VoIP and H.264/AVC video over IEEE 802.16d and IEEE 802.11g

We evaluate the capacity of an IEEE 802.16d and IEEE 802.11g testbed to simultaneously carry emulated H.264/AVC video and Speex VoIP and present results from an extensive measurement study. First, we employ two fixed WiMAX subscriber stations and one base station and report results for packet loss and one-way delay under both line-of-sight and non-line-of-sight conditions. In addition, we put these results in perspective by repeating the experiments using an off-the-self IEEE 802.11g router. In particular, we use the IEEE 802.11g access point as an extension to the WiMAX network, a case often considered in simulation studies. Finally, we consider the IEEE 802.11g access network in isolation, and measure its capacity to carry video streams and emulated bidirectional VoIP calls simultaneously and compare it with the WiMAX access network.

Performance of LTE uplink for IoT backhaul

The number of devices connected to the Internet is growing substantially as a result of increased realization of the Internet of Things (IoT) concept. As cellular networks can already be perceived almost as ubiquitous, they can potentially provide IoT systems access to the Internet regardless of their location. However, increased use of commercial cellular networks to provide connectivity for IoT systems would also change the traffic mix of these networks. It has been measured earlier that a large number of small packets are challenging for different wireless access networks to provide high performance. Currently, small packets are transmitted, for example, with Voice over IP (VoIP) services. Many IoT applications, being based on constrained sensor devices and Machine-to-Machine (M2M) type of communications, can increase the number of small packets significantly. In this paper, we measure the performance of Long Term Evolution (LTE) uplink as a backhaul for IoT networks. We experiment with differently sized packets in order to find optimal packet sizes that can result in maximum utilization of available resources in the LTE air interface. To the best of our knowledge, this is the first paper to thoroughly evaluate LTE uplink performance with different packet sizes based on empirical evidence. The results indicate that with very small packets the throughput performance is less than half from that obtained with large packets. As an application to exploit the achieved results, we propose IoT gateway solutions to perform packet aggregation at mobile edge to maximize resource utilization in the air interface.

Empirical Evaluation of Mobile WiMAX with MIMO

Mobile WiMAX is claimed to have the greatest potential of all wireless access technologies already in the markets with respect to network capacity, range, mobility, and quality of service support. Mobile WiMAX has also adopted MIMO as an essential element for increasing capacity and data propagation reliability. However, there are few publicly available studies demonstrating what is possible with Mobile WiMAX in practice and none that empirically evaluates the performance gains attained with MIMO. We fill this gap by comparing spacetime coding based 2x2 MIMO with single antenna mode in our Mobile WiMAX testbed. We conduct thorough measurements that involve vehicular mobility with different types of traffic. We find that MIMO significantly increases the reliability of data propagation over the wireless link, which is particularly evident when we consider TCP traffic. Since 3GPP LTE, the main rival to Mobile WiMAX, equipment and publicly deployed networks are yet to become available, HSPA and the soon-tobe-deployed HSPA+ amendments to UMTS are the only wireless technologies challenging Mobile WiMAX. Thus, we also compare Mobile WiMAX with HSPA, providing the first publicly available side-by-side measurement study.

IPTV over WiMAX with MIPv6 Handovers

As the IPv4 unallocated address pool nears exhaustion, an increasing number of IPv6 deployments is anticipated. In the domain of mobility management research and development, mobile IPv6 has long been favored over mobile IPv4. Nevertheless, although in principle WiMax supports IPv6 in various configurations and requires MIPv6 for network-level mobility management, in practice, vendors are actively deploying these capabilities only in part. This paper provides a thorough review of the role of IPv6 and MIPv6 in WiMax networks, surveying the work in relevant standardization bodies. The second contribution of this paper is a testbed evaluation of IPTV streaming over WiMAX. We employ two WiMax testbeds deployed in Finland and Portugal, interconnected by GEANT and quantify MIPv6 performance in a real-time multimedia streaming scenario over WiMAX. Beyond demonstrating the feasibility of such a deployment, our results indicate that WiMAX can provide a viable option as both access and backhauling technology.

Multi-client video streaming over wirelessMAN-OFDMA

Wireless Interoperability for Microwave Access (WiMAX) is a prime contender in the Broadband Wireless Access (BWA) market due to its next generation network architecture, low patent portfolio load considerations, support for Quality of Service (QoS), and last but not least, high capacities. Although until recently there has been a lot of interest in the mobility support of the technology, with the recent push for the Third Generation Partnership Projects (3GPP) Long Term Evolution (LTE), vendors are advancing WiMAX (in particular with the Wireless Metropolitan Area Network - Orthogonal Frequency Division Multiple Access (WirelessMAN-OFDMA) air interface specified by the IEEE 802.16 working group) as a fixed broadband replacement. For this market segment, Audio/Video (A/V) delivery is expected to be a key service offering. In this paper, we perform a detailed empirical evaluation using a state-of-the-art WiMAX testbed with multiple video flows directed at several Customer Premises Equipment (CPE) devices simultaneously. We employ the Evalvid framework and develop a methodology for its use in multi-client evaluations. We report our results for Variable Bit Rate (VBR) and Constant Bit Rate (CBR) video streams and draw conclusions.

DockingAssist: A novel vessel navigation system design based on WiMAX and DGNSS

The DockingAssist system is a centralised, cost-effective, real-time navigation system that provides the necessary centimetre positioning and speed accuracy to ensure efficient and safe manoeuvring within a entire port area, thereby enhancing vessel trajectory and providing constant monitoring of moored/docked vessels. By reducing transit, this system will result in improved port traffic management and lower operating expenses, CO2 emissions and fuel usage, thereby lessening the environmental impact of shipping. The reduced transit time will increase throughput in ports with a low investment. Our solution is based on WiMAX technology transmitting DGNSS positioning data in harbours. We provide proof-of-concept results based on empirical measurements performed in a real harbour. We find that WiMAX fulfils the requirements for accurate vessel positioning and navigation in harbour environment while providing wireless network capacity also for other services.