Mika Rinne

Device-to-device communication as an underlay to LTE-advanced networks

In this article device-to-device (D2D) communication underlaying a 3GPP LTE-Advanced cellular network is studied as an enabler of local services with limited interference impact on the primary cellular network. The approach of the study is a tight integration of D2D communication into an LTE-Advanced network. In particular, we propose mechanisms for D2D communication session setup and management involving procedures in the LTE System Architecture Evolution. Moreover, we present numerical results based on system simulations in an interference limited local area scenario. Our results show that D2D communication can increase the total throughput observed in the cell area.

Device-to-Device Communications; Functional Prospects for LTE-Advanced Networks

In this paper the possibility of device-to-device (D2D) communications as an underlay of an LTE-A network is introduced. The D2D communication enables new service opportunities and reduces the eNB load for short range data intensive peer-to-peer communication. The cellular network may establish a new type of radio bearer dedicated for D2D communications and stay in control of the session setup and the radio resources without routing the user plane traffic. The paper addresses critical issues and functional blocks to enable D2D communication as an add-on functionality to the LTE SAE architecture. Unlike 3G spread spectrum cellular and OFDM WLAN techniques, LTE-A resource management is fast and operates in high time-frequency resolution. This could allow the use of non-allocated time-frequency resources, or even partial reuse of the allocated resources for D2D with eNB controlled power constraints. The feasibility and the range of D2D communication, and its impact to the power margins of cellular communications are studied by simulations in two example scenarios. The results demonstrate that by tolerating a modest increase in interference, D2D communication with practical range becomes feasible. By tolerating higher interference power the D2D range will increase.

Channel equalization in filter bank based multicarrier modulation for wireless communications

Channel equalization in filter bank based multicarrier (FBMC) modulation is addressed. We utilize an efficient oversampled filter bank concept with 2x-oversampled subcarrier signals that can be equalized independently of each other. Due to Nyquist pulse shaping, consecutive symbol waveforms overlap in time, which calls for special means for equalization. Two alternative linear low-complexity subcarrier equalizer structures are developed together with straightforward channel estimation-based methods to calculate the equalizer coefficients using pointwise equalization within each subband (in a frequency-sampled manner). A novel structure, consisting of a linear-phase FIR amplitude equalizer and an allpass filter as phase equalizer, is found to provide enhanced robustness to timing estimation errors. This allows the receiver to be operated without time synchronization before the filter bank. The coded error-rate performance of FBMC with the studied equalization scheme is compared to a cyclic prefix OFDM reference in wireless mobile channel conditions, taking into account issues like spectral regrowth with practical nonlinear transmitters and sensitivity to frequency offsets. It is further emphasized that FBMC provides flexible means for high-quality frequency selective filtering in the receiver to suppress strong interfering spectral components within or close to the used frequency band.

LTE, the radio technology path towards 4G

Evolved Universal Terrestrial Radio Access (EUTRA), known as the Long Term Evolution (LTE) technology, brings cellular communication to the fourth generation (4G) era. In this article, we discuss the most important characteristics of LTE; its simplified network architecture which allows ultimate means for adaptation of the radio transmission to the Internet packet traffic flows and to the varying channel states. LTE radio resource management is based on time-frequency scheduling, fast feedback between the transmitter and receiver, and nearly optimal adaptation of transport formats. Yet, the radio system is simple and cost efficient to manage from the evolved packet core network, having a server architecture with IP tunnels. The mobility states and resource allocation allow power save operation of the User Equipment when not actively communicating. In addition, we brief the key results on the LTE baseline performance for paired and unpaired frequency bands, i.e. the two duplex modes.

Frequency-domain equalization in single-carrier transmission: filter bank approach

This paper investigates the use of complex-modulated oversampled filter banks (FBs) for frequency-domain equalization (FDE) in single-carrier systems. The key aspect is mildly frequency-selective subband processing instead of a simple complex gain factor per subband. Two alternative low-complexity linear equalizer structures with MSE criterion are considered for subband-wise equalization: a complex FIR filter structure and a cascade of a linear-phase FIR filter and an allpass filter. The simulation results indicate that in a broadband wireless channel the performance of the studied FB-FDE structures, with modest number of subbands, reaches or exceeds the performance of the widely used FFT-FDE system with cyclic prefix. Furthermore, FB-FDE can perform a significant part of the baseband channel selection filtering. It is thus observed that fractionally spaced processing provides significant performance benefit, with a similar complexity to the symbol-rate system, when the baseband filtering is included. In addition, FB-FDE effectively suppresses narrowband interference present in the signal band.

Analysis of the adaptive modulation and coding algorithm with the multicode transmission

Adaptive modulation and coding (AMC) has gained a lot of attention in the research targeting for the standardization of the high speed downlink packet access (HSDPA). The idea is to adapt the transmission to the fast changing channel conditions by the use of different modulation and coding schemes (MCS). In this paper, an algorithm is presented for the AMC technique in the HSDPA concept with multicode transmission, and the mathematical analysis of this algorithm is given. Furthermore, a scheduling algorithm is introduced in which the terminal in a queue with the best expected carrier-to-interference ratio (C/I) is selected for the transmission interval. Such maximum C/I scheduling with the AMC and multicode transmission is anticipated to increase the throughput. In this paper, the numerical results of the analysis are compared to the respective results obtained by the simulations.

A Performance Summary of the Evolved 3G (E-UTRA) for Voice Over Internet and Best Effort Traffic

Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (E-UTRA) is a new technology that targets the long-term evolution (LTE) of third generation. The E-UTRA technology has recently been standardized by the Third-Generation Partnership Project (3GPP) as a set of (series_36) specifications. The standardization process is almost complete; this paper does not focus on comparing specific proposed schemes but instead aims to outline the system performance more in general. E-UTRA operates in the packet-switched domain; hence, all traffic is handled by the packet protocols. The analysis is shown for Voice over Internet Protocol (VoIP) and Best Effort (BE) data, as these are common examples of real-time and non-real-time traffic, respectively. The performance is given in the VoIP study as the number of satisfied voice users per cell and in the BE study as the cumulative probability distribution of user (or cell) throughput, which was scaled to the spectral efficiency values, given both at the mean and at the cell edge. The VoIP capacity extends beyond 350 users in downlink and 230 users in uplink, which is a considerable increase compared with the high-speed packet-access (HSPA) reference. The BE spectral efficiency meets the 3GPP targets and yields impressive gains of order 2.5-3 times the well-performing HSPA reference. This clearly exceeds the mean of 1.5 b/s/Hz/cell in downlink and 0.8 b/s/Hz/cell in uplink for a baseline antenna configuration with penetration loss of 20 dB. In some scenarios, these mean gains exceed four times the reference.

Mixed traffic packet scheduling in UTRAN Long Term Evolution Downlink

In this paper we study the packet scheduling of mixed traffic in UTRAN long term evolution downlink. A dynamic packet scheduling (PS) architecture with service classification, queue specific sorting and scheduling algorithms as well as frequency domain PS has been presented to differentiate scheduling of different traffic classes. Simulation results have been provided by using control data, voice-over-IP (VoIP) and best effort (BE) traffic types. The results show that VoIP prioritizing is needed to keep the VoIP UEs satisfied. However, the strict prioritizing decreases the system spectral efficiency to around 70-80% of the pure BE spectral efficiency due to small VoIP packets.

The effect of code-multiplexing on the high speed downlink packet access (HSDPA) in a WCDMA network

The high-speed downlink packet access (HSDPA) is currently an important research topic to enhance the downlink performance of a WCDMA network. It is a set of schemes built on top of the downlink shared channel (DSCH), resulting an extremely high bit rate for a single user in the downlink. When the channel condition is good, a high utilization of the code resource for a single user can be effectively achieved. However, when the channel condition is bad, a fraction of the code resource would be wasted because only a user can use a small fraction of the code resource. Thus, code multiplexing offers a solution to utilize the limited code resource more effectively. In this paper, the effect of code multiplexing on the HSDPA performance is studied in a dynamic simulator platform. It means that the code resource is shared among a few users. Multicode transmission is also considered in the study. Two, semi-static and dynamic code sharing, multiplexing cases are studied. The number, n, of the code multiplexing users is one of the study parameters. The simulation results show that code-multiplexing can increase the throughput in a WCDMA network by improving code utilization while also decreasing the transfer delay between the base station and the terminals.

Performance analysis of GSM traffic channel capacity with(out) high speed circuit switched data

Analytical techniques for GSM traffic channel capacity analysis are studied. The results are represented for high speed circuit-switched data (HSCSD) traffic channels co-existing with voice traffic channels in a GSM cell. In a GSM system the base station has a finite number of traffic channels, from which one voice terminal occupies one traffic channel. The admission priority for voice services is higher than that of the HSCSD data. On the other hand, one HSCSD terminal can occupy a multiple number of channels if needed, provided that they are available. The HSCSD terminal will release its reserved traffic channels only after the data transmission is completed. The presence of HSCSD services slightly increases the blocking probability of the voice terminals. The results in this paper show the steady-state channel utilization and blocking probability of voice terminals under the constraints where voice terminals occupy one traffic channel at a time and data terminals can occupy multiple number of traffic channels. The results show that for a defined acceptable voice blocking probability, the overall channel utilization increases with the higher number of HSCSD terminals allowed per base station as well as with the higher number of channels allowed to be allocated for each HSCSD terminal. The traffic channel utilization also increases if the acceptable blocking probability for voice terminals is allowed to increase. The analytical model represented herein is general. Therefore, the channel utilization and the voice blocking probability results are calculated both with/without the HSCSD traffic channels. These numerical cases can be obtained by appropriate parameter setting from the same process model.