Esa Tapani Tiirola

5G small cell optimized radio design

The 5th generation (5G) of mobile radio access technologies is expected to become available for commercial launch around 2020. In this paper, we present our envisioned 5G system design optimized for small cell deployment taking a clean slate approach, i.e. removing most compatibility constraints with the previous generations of mobile radio access technologies. This paper mainly covers the physical layer aspects of the 5G concept design.

EUTRAN Uplink Performance

Alongside with on-going further WCDMA development, work on evolved universal terrestrial radio access network (EUTRAN), also known as long term evolution (LTE), has been initiated in 3GPP. The objective of EUTRAN is to develop a framework for the evolution of the 3GPP radio-access technology towards wider bandwidth, lower latency and packet-optimized radio-access technology with peak data rate capability up to 100 Mbps. For the uplink direction, single carrier-FDMA (SC-FDMA) has been chosen as the multiple access technology. This paper introduces the uplink technology, the current state of progress in 3GPP as well as expected schedule for actual specification availability and describes a couple of key features, channel dependent frequency domain scheduling and multi-user MIMO in more detail. System performance results for channel dependent frequency domain scheduling are presented as well

Centimeter-Wave Concept for 5G Ultra-Dense Small Cells

Ultra-dense small cells are foreseen to play an essential role in the 5th generation (5G) of mobile radio access technology, which will be operating over different bands with respect to established systems. The natural step for exploring new spectrum is to look into the centimeter-wave bands as well as exploring millimeter-wave bands. This paper presents our vision on the technology components for a 5G centimeter-wave concept for ultra-dense small cells. Fundamental features such as optimized short frame structure, multi-antenna technologies, interference rejection, rank adaptation and dynamic scheduling of uplink/downlink transmission are discussed, along with the design of a novel flexible waveform and energy-saving enablers.

Combining space-time block coding with diversity antenna selection for improved downlink performance

A closed-loop method combining N-out-of-M antenna selection and space-time block coding from the selected antennas is proposed and studied in this paper. Performance is evaluated for WCDMA parameters in both frequency nonselective Rayleigh fading channels and in frequency selective (Vehicular A) channels. Operation in intra- and inter-cell dominant interference scenarios is considered. Numerical results show that the additional antenna selection procedure brings a supplementary uncoded BER performance improvement in the range of approximately 2-3.5 dB for flat-fading channels and 0.8-1.5 dB for frequency selective channels (@BER=12%). A suboptimum selection scheme requiring only a single bit for antenna selection is also presented. In addition, the impact on performance of errors in the feedback channel is investigated in this paper.

Achieving low latency and energy consumption by 5G TDD mode optimization

The target for a new 5G radio access technology is to support multi-Gbps and ms latency connectivity simultaneously at noticeably lower energy consumption and cost compared to the existing 4G technologies, such as LTE-Advanced. Extremely short air interface latency is required to achieve these requirements in a TDD-based local area network. In this paper, we discuss how the required short TDD latency can be achieved and further utilized in 5G physical air interface. First, we investigate the enablers and limits of TDD latency by analyzing the performance of OFDM in different channel environments and discussing on the consequent frame length limits. We then provide a description on how the achieved short TDD latency can further be utilized to enable remarkably low energy consumption. A numerical analysis comparing the battery life time of the suggested 5G TDD air interface and LTE is provided, showing remarkable gains for the 5G air interface concept.

B4G local area: High level requirements and system design

A next generation Beyond 4G (B4G) radio access technology is expected to become available around 2020 in order to cope with the exponential increase of mobile data traffic. In this paper, research motivations and high level requirements for a B4G local area concept are discussed. Our suggestions on the design of the B4G system as well as on the choice of its key technology components are also presented.

Utran Long Term Evolution in 3GPP

The 3rd Generation Partner Ship Project (3GPP) produced the first version of WCDMA standard in the end of 1999, which is the basis of the Universal Mobile Telephone System (UMTS) deployed in the field today. This release, called release 99, contained all the basic elements to meet the requirements for IMT-2000 technologies. Release 5 introduced the high speed downlink packet access (HSDPA) in 2002, enabling now more realistic 2 Mbps and even beyond with data rates up to 14 Mbps. Further Release 6 followed with high speed uplink packet access (HSUPA) in end of 2004, with market introduction expected in 2007. Alongside with on-going further WCDMA development, work on evolved universal terrestrial radio access (UTRA) has been initiated in 3GPP. The objective of evolved UTRA is to develop a framework for the evolution of the 3GPP radio-access technology towards wider bandwidth, lower latency and packet-optimized radio-access technology with peak data rate capability up to 100 Mbps. This paper introduces the requirements, the current state of progress in 3GPP, findings on the performance, agreed architecture as well as expected schedule for actual specification availability

Vision for Beyond 4G broadband radio systems

Mobile communication systems have evolved over the past decades and each new generation brought new experience to the users enabled by technology innovations, while keeping some well established principles from previous generations. This trend continued up to LTE (Long Term Evolution) Advanced, the predominant 4th generation system which has just been standardized in 3GPP and is being rolled out soon. How will this trend continue to future systems which will be deployed in some 10 years from now which will be advanced enough to be called “Beyond 4G” (B4G)? This article presents how such B4G systems will look like and some key technologies they will rely on including versatile numerology, massive virtual MIMO from many base stations, both centralized and distributed architectures using fiber optics as backbone, advanced interference mitigation, cognitive self organization, and wideband RF radios.

Full-duplex self-backhauling for small-cell 5G networks

We consider in-band self-backhauling for small cell 5G systems. In-band self-backhauling enables efficient usage of frequency resources. When coupled with a flexible frame format, it also enables efficient time-division duplexing of uplink, downlink, and backhaul transmissions. Self-backhauling is particularly efficient when coupled with FD relaying. Antenna design, as well as cancellation in radio frequency and digital domains at an FD relay enables reuse of the same resources for backhaul and access hops. The use of radio resources in the self-backhauling and access hops can be coordinated to maximize end-to-end performance. We evaluate FD in-band self-backhauling in indoor 5G scenarios, targeting mobile broadband and ultrareliable communication use cases. Self-backhauling shows considerable promise for reaching 5G targets in these scenarios.

Performance evaluation of fixed-beam beamforming in WCDMA downlink

This paper studies downlink beamforming applied to the WCDMA system. The downlink performance of single-antenna transmission in a base station (BS) sector with 120/spl deg/ (reference case) is compared to the beamforming with a fixed-beam antenna array having two beams. The paper consists of link level simulations and the analysis of the simulation results. The performance is studied by using the so-called G-modelling principles, where G denotes geometry. Simulation results indicate that the fixed-beam approach could offer feasible coverage and capacity extension especially in macro cell environments. The downlink performance of a beamforming WCDMA BS deteriorates significantly in environments with large angular spread.