Kari Rikkinen

Network Coding and User Cooperation for Streaming and Download Services in LTE Networks

Publisher Summary This chapter proposes the usage of network coding and user cooperation for existing LTE networks. Long Term Evolution (LTE) networks are supposed to use Raptor codes for content distribution such as download and streaming services over the air towards mobile devices. Like other FEC technologies, Raptor codes introduce redundancy which increases the total bandwidth of the system and also increase the energy consumption of mobile devices with good channel characteristics due to ongoing repair messages for devices with bad channel characteristics. Raptor codes substantially increase the perceived delay for each user which can be problematic, especially for streaming services. Therefore user cooperation with network coding is proposed to support streaming and download services in future mobile communication systems and overcoming the bandwidth and energy issues. The simulation results show that local retransmissions can save up to 80% of redundant information of the cellular link, as long as there are at least two cooperative mobile devices. The results also show that network coding can save more than half of the traffic in the short-range link as long as there are four devices in the cooperation cluster. Larger gains can be achieved by increasing the number of cooperating devices. To make the local retransmission in the short-range link more efficient, network coding is considered for the local retransmission and a local retransmission protocol is proposed. Reducing the traffic on the short-range link can reduce the overall energy consumption, as well as reduce the time that is needed to complete the exchange of packets locally, especially in dense traffic networks.

Modeling of UE-UE interference at 2.5 GHz WCDMA

This paper presents a new modeling approach for the derivation of the capacity reduction in WCDMA downlink due to mobile-to-mobile (UE-UE) interference. The assumed frequency usage scenario is the FDD UL/DL + additional FDD DL operation at 2.5 GHz band identified by ITU-WP8F. The similar approach can be utilized also with other frequency usage scenarios and radio systems where the UE-UE interference is present. The developed downlink capacity model takes into account the average interference from closely located, spectrally adjacent mobiles. The model assumes non-uniform user distribution and the power coupling due to basestation-to-basestation (BS-BS) interference has been introduced, as well. The recognition of these interference phenomena is important since unlike the BS-UE interference between operators the DE-LE interference is difficult or even impossible to eliminate with the network planning methods. Results indicate that the effect of user distribution, adjacent network loading, UE-UE propagation, cell sizes and the BS-BS isolation have to be taken into account when comparing the performance of radio systems where the UE-LE interference is present.

Radio resource management solutions for WCDMA FDD systems with asymmetric UL/DL carrier allocation

This paper concerns frequency division duplex cdma systems (WCDMA FDD, cdma2000, etc.) to which extension frequency bands might be added, e.g. for capacity enhancement reasons. Such asymmetric capacity enhancements might be desirable in the future due to increased data transmission over mobile networks especially when asymmetric data is transmitted like, for example, in mobile Internet browsing. Here it is assumed that the frequencies to be added are in downlink. In such a case the one-to-one coupling of uplink (or reverse link) and downlink (or forward link) frequencies is not valid any more. This paper illustrates a new interference scenario that can occur with the new downlink extension bands, and introduces new RRM (radio resource management) solutions for this interference case. The interference mechanism is illustrated for WCDMA. The assumed frequency scenario is WCDMA/FDD uplink/downlink plus additional FDD downlink, e.g. at 2.5 GHz band identified by ITU-WP8F. The new type of interference can be detected by additional mobile station measurements that benefit in efficiency from co-siting of extension and existing frequencies. Both interference detection and avoidance being based on RRM allows flexible and efficient use of extension bands with little impact on current specifications and products.

Key technologies and concepts for beyond-3G networks

Standardization of 3rd Generation (3G) mobile communication systems has produced the first specification releases and the commercial deployment of the 3G systems has started. Whereas 1G and 2G focused on efficiently providing voice services, in 3G a lot of attention has been devoted to solutions that support both Circuit Switched (CS) and Packet Switched (PS) communication. That has called for very flexible air interface and network solutions. 3G will continue to evolve and there are already on-going standardization activities that will, for example, boost the peak data rates up to 5-10 Mbps and improve spectral efficiency by 2-4 times. In the future, 3G evolution will be going towards 10/100 Mbps peak data rates in wide/local are coverage, respectively. This will take place partly because of technical improvements of 3G radio interface solutions, but also due to network evolution which will allow the integration other radio access methods like radio LANs into the 3G system. In longer term the 3G network evolution will be going towards ALL-IP networks. As 3G evolution seems to be going towards 10 Mbps/100 Mbps peak data rates and ALL-IP networks any beyond 3G air interface or network solution should be clearly better in order to justify its technical and commercial feasibility. Given the long evolution time of 3G and integration of other radio access schemes with 3G radio we may not even see a new, complete beyond 3G system being developed. Maybe we will just witness the emergence of a new, more advanced radio access solution which will then be connected to the evolving 3G network. As 3G evolution will continue for several years to come the research targets for any beyond 3G solutions must be set very high. When it comes to air interface, we should aim at 100 Mbps peak data rates for wide area access with high mobility, and at 1 Gbps for local area access with low mobility. Regarding possible commercial launches of any beyond 3G systems or solutions they could then take place around year 2010 or even later.