Kari Pajukoski

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.

LTE-Advanced: The path towards gigabit/s in wireless mobile communications

This paper addresses the performance targets and the technology components being studied by 3GPP for LTE-Advanced. LTE-Advanced is the next major step in the evolution of UTRAN Long Term Evolution (LTE) release 8, currently being finalized by 3GPP. The high level targets of LTE-Advanced are to meet or exceed the IMT-Advanced requirements set by ITU-R and furthermore, meet any additional operator requirements. This for instance includes the target of supporting more than one gigabit/s data rates, higher cell throughput and lower cost per bit. The technology components being identified as part of the LTE-Advanced Study Item include component carrier aggregation to enable up to 100MHz bandwidth, advanced MIMO options up to 8×8 in DL and 4×4 in UL, coordinated multiple point transmission and reception (CoMP), relay nodes (RN) and autonomous component carrier selection (ACCS) for uncoordinated femto cell deployment.

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.

Zero-tail DFT-spread-OFDM signals

In the existing scheduled radio standards using Orthogonal Frequency Division Multiplexing (OFDM) or Discrete Fourier Transform-spread-OFDM (DFT-s-OFDM) modulation, the Cyclic Prefix (CP) duration is usually hard-coded and set as a compromise between the expected channel characteristics and the necessity of fitting a predefined frame duration. This may lead to system inefficiencies as well as bad coexistence with networks using different CP settings. In this paper, we propose the usage of zero-tail DFT-s-OFDM signals as a solution for decoupling the radio numerology from the expected channel characteristics. Zero-tail DFT-s-OFDM modulation allows to adapt the overhead to the estimated delay spread/propagation delay. Moreover, it enables networks operating over channels with different characteristics to adopt the same numerology, thus improving their coexistence. An analytical description of the zero-tail DFT-s-OFDM signals is provided, as well as a numerical performance evaluation with Monte Carlo simulations. Zero-tail DFT-s-OFDM signals are shown to have approximately the same Block Error Rate (BLER) performance of traditional OFDM, with the further benefit of lower out-of-band (OOB) emissions.

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

Turbo Receivers for Single User MIMO LTE-A Uplink

The paper deals with turbo detection techniques for Single User Multiple-Input-Multiple-Output (SU MIMO) antenna schemes. The context is on the uplink of the upcoming Long Term Evolution - Advanced (LTE-A) systems. Iterative approaches based on Parallel Interference Cancellation (PIC) and Successive Interference Cancellation (SIC) are investigated, and a low-complexity solution allowing to combine interstream interference cancellation and noise enhancement reduction is proposed. Performance is evaluated for Orthogonal Frequency Division Multiplexing (OFDM) and Single Carrier Frequency Division Multiplexing (SC-FDM) as candidate uplink modulation schemes for LTE-A. Simulation results show that, in a 2times2 antenna configuration, the turbo processing allows a consistent improvement of the link performance, being SC-FDM the one having higher relative gain with respect to linear detection. The turbo receivers impact is however much reduced for both modulation schemes in a 2times4 configuration, due to the higher diversity gain provided by the additional receive antennas.

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.