Andres Arjona

Unlicensed Mobile Access (UMA) Handover and Packet Data Performance Analysis

UMA is a technology helping cellular operators to retain control over subscribers in the era of converging radio access technologies. By supporting handovers to and from WiFi networks, UMA seems to be a perfect solution as new mobile services require performance and seamless mobility. From the cellular operator point of view UMA does not require enormous investments and is a good choice for extending network coverage. This research paper discusses the technical implications of UMA based on measurement results for GSM to WiFi handovers and packet data performance. The measurements show that UMA works well, and voice handover breaks are similar or lower than those experienced in traditional GSM systems. In addition, UMA provides a considerably higher throughput than GSM systems. The results showed that the average throughput is twice or more than in GSM. Therefore, the user experience for data services improves to 3G-kind of services.

Towards High Quality VoIP in 3G Networks - An Empirical Study

Third generation (3G) packet switched WCDMA networks with high-speed downlink packet access (HSPDA) are currently being deployed worldwide to provide wireless broadband connectivity. When introducing HSDPA in 3G networks the end user experience and system capacity with voice over IP applications improve considerably. When later on adding also high-speed packet uplink access (HSUPA), the system capacity and end user experience will improve even further. This paper analyzes with measurements the VoIP quality over current Release 5 HSDPA networks. The results show that even though the introduction of HSDPA significantly reduces the user-to-user voice delay, the performance is satisfactory only for selected devices, the overall end user experience is still significantly worse than with circuit switched solutions and not acceptable. The current limitations with VoIP in HSDPA networks with a too large delay can be improved by using the RLC UNACK mode, potentially decreasing the jitter buffer size and reducing the terminal processing delay. In the longer term, HSUPA and several features in 3GPP Release 7 standards will bring further performance improvements in both user plane latency and system capacity.

The Google Muni Wifi Network--Can it Compete with Cellular Voice?

Muni WiFi deployments have been widely covered by the media during the last two years. However, the economical feasibility and performance of such deployments as an alternative for voice services has not been proven. In this paper we measure the voice performance and coverage of the Google network. Then we evaluate the economical feasibility versus cellular deployments. The results show that providing a good service level for voice requires a much more expensive investment. Thus, Googles network is not a competitor for cellular voice. In the current deployment, VoIP is possible only in static scenarios and coverage across the city is not adequate except for the downtown area. For this reason, even though it is possible to use VoIP services in certain locations, the voice quality is far from optimal except for areas with excellent signal conditions. Unfortunately, such areas are rare. Likewise, access points are not densely deployed and lack coverage overlapping. Therefore, it is not possible to provide mobility to VoIP services. In mobility scenarios, voice quality degrades when the wireless link weakens and eventually the call is dropped before reaching coverage from the adjacent access point.

Live Network Performance Challenge: FLASH-OFDM vs. HSDPA

HSDPA networks are intensively being deployed to provide mobile broadband connectivity to mobile devices. In addition to HSDPA, FLASH-OFDM is another wireless broadband option operating in a licensed spectrum. However, if operated at very low frequencies like the network in Finland,, it is particularly interesting for emerging markets, especially for rural areas which are lacking telecommunications infrastructure. In contrast to the HSDPA standards, the FLASH-OFDM systems are proprietary. The market dynamics are very different between standardized and proprietary systems, sometimes causing extra challenges for the deployment of proprietary systems. This paper provides quantitative measurements of the actual performance of two state-of-the-art live networks in Finland. The evaluation includes metrics such as throughput, delay, and VoIP quality considering network performance both on static and mobile scenarios. A commercial deployment evaluation is included in the analysis complementing the measurement data in order to provide a comprehensive view of the challenges.

Interconnecting multiple home networks services

Universal plug and play (UPnP) is a set of protocols for automatic service discovery in a local area network (LAN). UPnP is suitable for home networking environments, where consumers, e.g., can buy a new device, plug it into the network and the device automatically configures itself in order to access the resources of the network. UPnP can be used only in a single LAN because the UPnP protocols use link-local multicast to announce their presence and there is no global Internet-wide multicast backbone available for multicast service discovery. Consequently, the devices and services of one LAN will not be available to another LAN. In this paper we describe a solution for connecting multiple home networks and their UPnP-based services together over the public Internet, without relying on global multicast. We have implemented the solution and tested it using UPnP capable devices such as Nokia mobile phones and a PDA. We discuss the security of the system, e.g., how firewall rules can be set up in the gateway to allow only authorized hosts to access the devices and services.

VoIP Call Signaling Performance and Always-On Battery Consumption in HSDPA, WCDMA and WiFi

Wireless broadband enables the use of VoIP with handheld mobile deices. Likewise, multi radio terminals provide the user with ubiquitous access. Even though broadband access might be available in different locations, performance still depends on the wireless technology used. We study the main signaling delays that take place in a voice call (registration and voice call setup delays) and compare them for different wireless accesses: HSDPA, WCDMA and WiFi. Likewise, possible optimizations with always-on mode and their drawbacks are presented. Signaling delays and total battery lifetime affect the perceived end user experience directly, and thus are important items to consider in addition to the overall voice quality.

Can the current generation of wireless mesh networks compete with cellular voice

Wireless mesh networks are being deployed to provide broadband wireless connectivity to city-wide hotspots. The typical architecture in these deployments thus far is a single-radio architecture: mesh nodes carry only one radio, which is used both to receive the traffic from the clients and to relay this traffic through the mesh to the wired Internet gateway.In this paper, we study the performance of a representative single-radio mesh network both in a live setup and in a laboratory environment. We characterize the performance of different applications (e.g. VoIP), and study some key challenges of mesh networks such as the fairness in bandwidth allocation and hidden node terminal. Finally, we compare the results of the study with traditional cellular networks, and discuss various options to enhance the performance of wireless mesh networks in the future.

Data outage across 3G & 2G wireless networks

Service continuity between EGPRS (2G) and WCDMA (3G) systems has been identified as one key research item recently. Measurement from live cellular networks indicate that outage time for packet switched traffic during intersystem handovers are too long going up to one minute in some cases. In this article we analyze intersystem handover latency across 3G and 2G wireless networks. The inter-system handover focused on the service interruption during mobility using both of the main data protocols, TCP and UDP. The results showed that the data outage is high for TCP and UDP, up to 7s and 10s respectively and can considerably affect real-time user applications. Some proposals have been highlighted to improve handover performance including candidate features such as the packet switched handover feature in 3GPP Rel 7. The performance degradation mostly depends on the application type, transmission protocol, intersystem handover type, and bandwidth of the wireless access link.

Empirical analysis of the single-radio mesh architecture: performance limitations and challenges

Wireless mesh networks are being deployed to provide broadband wireless connectivity to city-wide hotspots. The most successful commercial architecture in these deployments thus far is a single-radio architecture: mesh nodes carry only one radio, which is used both to receive the traffic from the WiFi clients and to relay this traffic through the mesh to the wired internet gateway. In this paper, we study the performance of a representative single radio mesh network and evaluate several key quantities: the fairness in the bandwidth allocation, the impact of the hidden node terminal, and the number of concurrent VoIP supported by the network.

Mobile IP as an Enabling Technology for VoIP in Metropolitan Wireless Mesh Networks

Metropolitan wireless mesh networks are being deployed to provide broadband connectivity to city-wide hotspots. However, its commercial feasibility and business model have not yet proven successful. In particular, deploying large areas with good signal coverage is very difficult. The main problem is a result of the number of required nodes to cover an area with proper signal strength that can support services such as VoIP. Unfortunately, as the number of nodes increases, so does the cost of deployment. In an environment for which the economical model has not been proved, increasing the cost of deployment is not feasible. However, by the use of Mobile IP, it is possible to interwork with other networks. In this way, users can roam to other networks with broader coverage (e.g. 3G) in places where wireless mesh coverage is no longer available or suffers from coverage gaps. This paper, underlines the actual performance of the Mobile IP solution via actual measurements with available commercial handsets. The focus is on the feasibility of using VoIP services over wireless mesh networks and interwork with 3G networks. The results show that even though the performance is not yet optimal, it is ready for a service rollout under proper conditions. In particular, a good service offering can encourage users to make use of this technology despite the performance limitations.