SON for LTE-WLAN access network selection : design and performance

Mobile network operators (MNOs) are deploying carrier-grade Wireless Local Area Network (WLAN) as an important complementary system to cellular networks. Access network selection (ANS) between cellular and WLAN is an essential component to improve network performance and user quality-of-service (QoS) via controlled loading of these systems. In emerging heterogeneous networks characterized by different cell sizes and diverse WLAN deployments, automatic tuning of the network selection functionality plays a crucial role. In this article, we present two distinct Self-Organizing Network (SON) schemes for tuning the ANS between the Long-Term Evolution (LTE) and WLAN systems. The SON functions differ in terms of availability of inter-system information exchange and internal algorithm design for traffic load control. System level simulations in a site-specific dense urban network show that the proposed schemes improve significantly the user quality of service (QoS), and network capacity over the reference scheme when offloading to WLAN is performed simply based on signal coverage

Blind synchronization in asynchronous UWB networks based on the transmit-reference scheme

Ultra wideband (UWB) wireless communication systems are based on the transmission of a stream of narrow pulses (each shorter than a ns). In such a system it is of great importance to estimate the beginning of the data packet of interest in order to subsequently estimate the data symbols. In this paper we present a combined blind synchronization and detection scheme based on the transmit-reference ultra wideband (TR-UWB) transceiver model taking into account a channel with a long impulse response. The proposed algorithm processes a block of received data samples, takes advantage of a shift invariance structure in the frequency domain, and applies a MUSIC-like search to estimate the delay of the data packet. 1

Synchronization and detection for transmited reference UWB systems

In this paper we present a synchronization scheme for multiuser transmit-reference ultrawide band (TR-UWB) systems. The proposed blind deterministic synchronization algorithm delivers a fine resolution data packet offset estimate by processing blocks of the received data sequence. The complexity of the algorithm is considerably reduced by exploiting the property that a time domain shift corresponds to a phase rotation in frequency domain. In the simulations the whole transceiver chain is considered taking into account measured channel impulse responses in a typical university building. 1

Blind synchronization in multiuser transmit-reference UWB systems

Ultrawideband (UWB) or impulse radio wireless communication systems are based on the transmission of extremely narrow pulses, with a duration inferior to a nanosecond. By design, Transmit-Reference (TR) UWB systems can avoid channel estimation at the receiver, while different users can share the same available bandwidth by using different spreading codes, similar to CDMA systems. This allows the receiver to separate different users, but, more crucially, to recover timing information of the transmitted packets and thus achieve synchronization within a short, burst-like packet transmission. By recognizing that a shift in time corresponds to a phase rotation in the frequency domain, a blind synchronization algorithm that takes advantage of the shift invariance structure in the frequency domain is proposed in this paper, allowing for a fast, high-resolution packet offset estimation. 1

Blind Synchronization in Asynchronous UWB Networks Based on the Transmit-Reference Scheme

<p/> <p>Ultra-wideband (UWB) wireless communication systems are based on the transmission of extremely narrow pulses, with a duration inferior to a nanosecond. The application of transmit reference (TR) to UWB systems allows to side-step channel estimation at the receiver, with a tradeoff of the effective transmission bandwidth, which is reduced by the usage of a reference pulse. Similar to CDMA systems, different users can share the same available bandwidth by means of different spreading codes. This allows the receiver to separate users, and to recover the timing information of the transmitted data packets. The nature of UWB transmissions&#8212;short, burst-like packets&#8212;requires a fast synchronization algorithm, that can accommodate several asynchronous users. Exploiting the fact that a shift in time corresponds to a phase rotation in the frequency domain, a blind and computationally effcient synchronization algorithm that takes advantage of the shift invariance structure in the frequency domain is proposed in this paper. Integer and fractional delay estimations are considered, along with a subsequent symbol estimation step. This results in a collision-avoiding multiuser algorithm, readily applicable to a fast acquisition procedure in a UWB ad hoc network.</p

Blind synchronization in asynchronous UWB networks based on the transmit-reference scheme

Ultra-wideband (UWB) wireless communication systems are based on the transmission of extremely narrow pulses, with a duration inferior to a nanosecond. The application of transmit reference (TR) to UWB systems allows to side-step channel estimation at the receiver, with a tradeoff of the effective transmission bandwidth, which is reduced by the usage of a reference pulse. Similar to CDMA systems, different users can share the same available bandwidth by means of different spreading codes. This allows the receiver to separate users, and to recover the timing information of the transmitted data packets. The nature of UWB transmissions—short, burst-like packets—requires a fast synchronization algorithm, that can accommodate several asynchronous users. Exploiting the fact that a shift in time corresponds to a phase rotation in the frequency domain, a blind and computationally effcient synchronization algorithm that takes advantage of the shift invariance structure in the frequency domain is proposed in this paper. Integer and fractional delay estimations are considered, along with a subsequent symbol estimation step. This results in a collision-avoiding multiuser algorithm, readily applicable to a fast acquisition procedure in a UWB ad hoc network. Copyright © 2006 Relja Djapic et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1

Synchronization and packet separation in wireless ad hoc networks by known modulus algorithms

Abstract—In mobile asynchronous ad hoc networks, multiple users may transmit packets at the same time. If a collision occurs, then in current systems both packets are lost and need to be retransmitted, reducing the overall throughput. To mitigate this, we consider to extend the receiver with a small antenna array, so that it can suppress interfering signals. To characterize the signal of interest, we propose to modulate it at the symbol rate by a known amplitude variation. This allows the corresponding multichannel receiver to estimate the beamformer weights that will suppress the interfering sources. We introduce “known modulus algorithms” to achieve this. We also derive synchronization algorithms to estimate the offset of the desired packet in an observation window, among interfering data packets. The algorithms are illustrated via simulations. Index Terms—Ad hoc networks, blind source separation, known modulus algorithm (KMA), packet offset estimation, synchronization. I

Performance of SON for RSRP-based LTE/WLAN access network selection

Carrier-grade Wireless Local Area Network (WLAN) is becoming an important complementary system to cellular networks for Mobile Network Operators (MNOs). Network controlled access network selection between cellular and WLAN is an essential functionality to optimize network performance and user experience. Automated configuration and optimisation of the network selection mechanism is of utmost importance in the emerging complex heterogeneous networks. In this article, we present and evaluate a Self-Organizing Network (SON) scheme for optimizing autonomously the access network selection between the Long Term Evolution (LTE) and WLAN systems. The adopted access network selection mechanism uses the standard LTE Received Reference Signal Power (RSRP) measurements available at the User Equipment (UE) and a set of simple rules based on network-provided RSRP thresholds. The proposed SON mechanism is using the LTE cell load estimated at the evolved NodeB (eNB) to update the RSRP thresholds in order to achieve the best load balancing in the network. Simulation results in a realistic network highlight the benefits of the proposed SON mechanism and possible further improvements

Performance of WLAN RSS-based SON for LTE/WLAN access network selection

Mobile Network Operators (MNOs) are integrating carrier-grade Wireless Local Area Network (WLAN) to cellular networks to improve network performance and user experience. Access network selection (ANS) between cellular and WLAN plays a key role in the integration. Given the complexity of heterogeneous networks characterized by multiple network layer deployments and inhomogeneous traffic distribution, the ANS has to automatically adapt to dynamic network conditions. In this article, we present and evaluate a Self-Organizing Network (SON) algorithm for tuning the ANS between the Long Term Evolution (LTE) and WLAN systems. The proposed SON algorithm adopts a WLAN received signal strength (RSS) threshold to control the access selection. The RSS threshold is updated by the SON algorithm based on periodically monitored load in the LTE and WLAN systems. The SON algorithm is evaluated by simulations in realistic heterogeneous network scenarios and proved effective in improving user experience