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In the current IEEE 802.11 wireless LAN (WLAN), each station (STA) must obtain transmission opportunity (TXOP) on its primary channel. It means that current WLAN hardly utilizes the whole spectral resources in a frequency band if congestion occurs in some WLAN channels or bands. To overcome this problem, a concept of alternative primary channel (APCH) has been proposed. The APCH is a channel on which...
In this paper, we propose a low latency relay transmission scheme for WLAN which simultaneously uses multiple bands. In order to reduce the latency, the proposed relay transmission scheme forwards a bit sequence which is obtained by truncated decoding. In the proposed relay transmission scheme, a relay node receives a header of a frame on a frequency band. If relay transmission is required, the relay...
In this paper, we propose a synchronization scheme to obtain frequency diversity in a WLAN system which simultaneously uses the multiple bands such as 5 GHz, 2.4 GHz and 920 MHz simultaneously. The proposed scheme is to combine the output of correlators after compensation for the difference of the center frequency on each frequency band. The proposed scheme obtains a large frequency diversity gain...
The modified Luise and Reggiannini (L&R) algorithm is one of the frequency offset estimation algorithms suitable for use with the Digital Video Broadcasting — Satellite (DVB-S2) standard. Recently we demonstrated an enhanced poly-polarization multiplexing (EPPM) system incorporating L&R frequency recovery as a hardware prototype in order to evaluate its high spectral-efficiency in a real satellite...
We have proposed a concept of a new Quality of Experience (QoE) oriented wireless local area network (WLAN) on which many applications can run with sufficient quality even in congested environment. The proposed system is designed by taking users’ QoE as a key metric. In this paper, we propose a practical functional flow featuring a new channel access control scheme based on loadable capacity prediction...
This paper proposes a method to reduce the symbol error caused by modulo operator for regularized channel inversion (RCI)-based vector perturbation (RCI-VP). The proposed method introduces dual regularization parameters of RCI precoding matrix. First regularization parameter a\ is set so as to maximize the signal to interference plus noise ratio (SINR) value of each stream to find the optimal perturbation...
We have recently implemented a poly-polarization multiplexing (PPM) system as a hardware prototype in order to demonstrate its high spectral-efficiency in a satellite channel. The Luise and Reggiannini (L&R) algorithm is one of the frequency offset estimation methods suitable for use with the Digital Video Broadcasting — Satellite (DVB-S2) standard, and has also been implemented in our PPM receiver...
Frequency recovery is a critical element in virtually all high data-rate communications systems, and in order to enhance the performance of our recently proposed poly-polarization multiplexing (PPM) satellite system, we have investigated the performance benefits of distributing the unique word (UW) symbols. The mean square error is calculated for different correlation based algorithms with increasing...
A poly-polarization multiplexing (PPM) scheme, that simultaneously utilizes two orthogonal polarization signals to create virtual additional planes, has been studied to enhance the spectrum efficiency for fixed satellite communication in the Ku band (12, 14 GHz). In this paper, to further increase the spectrum efficiency, we propose an enhanced PPM (E-PPM) scheme. By formulating the generalized linear...
We have developed an LTE-Advanced-based 8 × 8 multiuser MIMO experimental system with vector perturbation to overcome performance degradation of the MIMO technique under spatially correlated channel conditions, such as a line-of-sight (LoS) environment. This paper introduces our experimental system and shows results of outdoor/indoor experiments envisioning small-cell environments. Through experimental...
In this paper, we propose a Quality of Experience based autonomously distributed wireless system for medical and disaster situation. The radio resource assignment and topology are dynamically controlled based on QoE of each application. First of all, we show a situation of 2.4 GHz wireless system environment in a major hospital, and raise some issues of spectrum usage in medical area from the measurement...
This paper proposes a new dynamic and reconfigurable M2M wireless network, which is aimed to be applicable for medical system and for emergency situations. We identify issues for realising efficient operation of applications on the proposed system, and show our technical solutions. In particular, we propose to introduce new metrics for managing the wireless network, which are enhanced user QoE. With...
This paper proposes a method to improve the performance of minimum-mean square error (MMSE) based vector perturbation (MMSE-VP) by introducing dual regularization parameters of MMSE precoding matrix. First regularization parameter a1 is set so as to maximize the signal to interference plus noise ratio (SINR) value of each stream to find the optimal perturbation vector. The second regularization parameter...
During the operation of multiuser multiple-input-multiple output (MU-MIMO) algorithms, some antennas of BS or UEs may neither transmit nor receive signals due to the long distance or unexpected damages. Therefore, the BS cannot obtain the channel state information (CSI) from/to these antennas. Without these CSI, the performance of algorithm is degraded. We call this effect as ‘broken antenna effect...
A single carrier transmission system is proposed. It is a dynamic spectrum access system designed for ISM bands where various radio systems are operating. The proposed system divides the spectrum of the single carrier modulation into a few ??subspectra?? and allocates them for fragmented vacant spectra, which are called ??white space?? in the band. Not FFT/IFFT operations for each signal block with...
To improve the area throughput of OFDM-based IEEE 802.11 wireless LAN systems in an OBSS environment, this paper proposes a new overlay transmission protocol which does not require any signal/frame exchange prior to DATA frame transmission. The proposed protocol introduces a new field which containing a portion of the BSSID to which the destination node belongs in order to indicate who must listen...
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