Wireless access system

1. Field of the Invention

The present invention relates to a wireless access system using a space-division multiple access communication as multiple wireless communication.

2. Discussion of the Related Art

Conventionally, as disclosed in Japanese Patent No. 3926669, a wireless access system including a wireless control station and at least one wireless terminal device is known, in which the wireless control station transmits data in compliance with each of the wireless terminal devices through space-division multiple access communication. Meanwhile, data transmission to a wireless terminal device located in each directional space divided by space-division multiple access communication control is exclusively permitted, and time-division data are transmitted to the wireless control station while the wireless terminal device is permitted to transmit data by the wireless control station.

In the conventional wireless access system, data are transmitted from the wireless control station to the wireless terminal device through space-division multiple access communication in down transmission, and from the wireless terminal device to the wireless control station through time-division multiple access communication in up transmission. Therefore, in multiple access communication between the wireless control station and the wireless terminal device, interference between wireless transmission signals from the wireless terminal device is prevented, and interference waves at the wireless control station do not need removing.

However, multiple access communication between plural wireless control stations and wireless terminal devices is not considered.

In particular, a feasible technology for sharing one wireless terminal device among plural wireless control stations and controlling access is not disclosed.

Accordingly, an object of the present invention is to provide a wireless access system capable of preventing interference with wireless transmission signals between the wireless control stations without needing removal of interference waves in the wireless terminal device in multiple wireless communication between plural wireless control stations and wireless terminal devices.

Another object of the present invention is to provide a wireless terminal device.

A further object of the present invention is to provide a wireless access method.

To achieve such objects, the present invention contemplates the provision of a wireless access system, comprising:

plural wireless control stations;

a wireless terminal device to transmit and receive data to and from the plural wireless control stations,

wherein the wireless control stations adjust with each other to reserve data transmission periods so as not to overlap with those of the other wireless control stations and transmit data in the reserved periods, and

the wireless terminal device transmits data to at least one of the wireless control stations through space-division multiple access communication.

These and other objects, features and advantages of the present invention will become apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.

FIG. 1 is a block diagram of an embodiment of the wireless access system of the present invention;

FIG. 2 is a block diagram of a WUSB device constituting the embodiment of the wireless access system of the present invention;

FIG. 3 is a block diagram of a WUSB host constituting the embodiment of the wireless access system of the present invention;

FIG. 4 is a timing diagram of a first operational example of the embodiment of the wireless access system of the present invention; and

FIG. 5 is a timing diagram of a second operational example of the embodiment of the wireless access system of the present invention.

Generally, the present invention provides a wireless access system largely improving communication capacity through space-division multiple access communication when transmitting from a wireless terminal in multiple wireless communication between plural wireless control stations and wireless terminal devices and preventing interferences between wireless transmission signals from the wireless control station when transmitting to need no removal of interference waves in the wireless terminal device. More particularly, the present invention relates to a wireless access system, comprising:

plural wireless control stations;

a wireless terminal device to transmit and receive data to and from the plural wireless control stations,

wherein the wireless control stations adjust with each other to reserve data transmission periods so as not to overlap with those of the other wireless control stations and transmit data in the reserved periods, and

the wireless terminal device transmits data to at least one of the wireless control stations through space-division multiple access communication.

As shown in FIG. 1 , an embodiment of the wireless access system of the present invention includes a WUSB device 2 and plural WUSB hosts 3 a to 3 c . In FIG. 1 , three WUSB hosts 3 a to 3 c are shown, but the number of the WUSB hosts is not limited thereto.

The WUSB device 2 represents the wireless terminal device of the present invention, and includes peripheral equipment such as combined machines, printers and projectors. Each of the WUSB hosts 3 a to 3 c represents the wireless control station of the present invention, and includes a versatile personal computer capable of communicating with WUSB.

As shown in FIG. 2 , the WUSB device 2 includes a main unit system 10 to control a main unit of peripheral equipment such as combined machines, printers and projectors, and a WUSB device communicator 11 to transmit and receive data to and from each of the WUSB hosts 3 a to 3 c.

The WUSB device communicator 11 includes a main system 10 , a system IF 12 which inputs and outputs data, a SDMA transmitter 13 which transmits data to each of the WUSB hosts 3 a to 3 c through space-division multiple access (SDMA) communication and a TDMA receiver 14 which receives data transmitted from each of the WUSB hosts 3 a to 3 c through time-division multiple access (TDMA) communication.

The SDMA transmitter 13 includes media access control (MAC) transmitters 20 a to 20 d , baseband (BB) transmitters 21 a to 21 d , a SDMA transmission processor 22 and antenna elements 23 a to 23 d.

In FIG. 2 , each four MAC transmitters 20 a to 20 d , BB transmitters 21 a to 21 d and antenna elements 23 a to 23 d are shown, but the numbers thereof are not limited thereto.

Each of the MAC transmitters 20 a to 20 d subject data input from the main system 10 through the system IF 12 to a transmission process relating to MAC layer and output the processed data to the BB transmitters 21 a to 21 d , respectively.

The BB transmitters 21 a to 21 d modulate the data input from the MAC transmitters 20 a to 20 d to BB signals, respectively. The SDMA transmission processor 22 duplicates each of the BB signals to the number of the transmission antenna elements, multiplies the BB signal by an adjustment factor relating to an amplitude and a phase in the direction of the WUSB hosts 3 a to 3 c to up-convert the signal to a radio frequency (RF) signal, and transmits the RF signals as electric waves through the antenna elements 23 a to 23 d , respectively.

In FIG. 1 , same signals only different in amplitude and phase are transmitted from the four antenna elements, and a directive signal in the direction of the WUSB host 3 a is synthesized in a space. When adjustment factor relating to an amplitude and a phase in the direction of the WUSB hosts 3 b and 3 c , a directive signal is synthesized as well.

The electric waves transmitted from each of the antenna elements 23 a to 23 d are synthesized in a space and transmitted to directional spaces 4 a to 4 c , respectively as FIG. 1 shows. At least one of the antenna elements 23 a to 23 c is located at least one of directional spaces 4 a to 4 c.

In FIG. 2 , the TDMA receiver 14 includes a an antenna 30 , an RF receiver 31 which down-converts an RF signal received through the antenna 30 to a BB signal, a BB receiver 32 which demodulates the BB signal and a MAC receiver 33 which subjects the demodulated data to a reception process relating to MAC layer and outputs the data to the main system 10 through the system IF 12 . The TDMA receiver 14 can share the antenna elements 23 a to 23 d instead of the antenna 30 by time-division with the SDMA transmitter 13 .

Each of the WUSB hosts 3 a to 3 c (hereinafter referred to as “WUSB host 3 ” collectively) include, as shown in FIG. 3 , a main system 40 which performs a process relating to a layer prior to the MAC layer, a WUSB host communicator 41 for transmitting and receiving data to and from a WUSB device 2 , and an antenna 42 .

The WUSB host communicator 41 includes a system IF 43 which inputs and outputs data with the main system 40 , a transmitter 44 which transmits data to the WUSB device 2 through TDMA communication and a receiver 45 which receives a directional space signal transmitted from the WUSB device 2 through TDMA communication to its own station.

The transmitter 44 includes a MAC transmitter 50 , a BB transmitter 51 and an RF transmitter 52 . The MAC transmitter 50 subjects data input from the main system 40 through the system IF 43 to a transmission process relating to MAC layer and outputs the processed data to the BB transmitter 51 .

The BB transmitter 51 modulates data input from the MAC transmitter 50 to a BB signal. The RF transmitter 52 up-converts the BB signal to an RF signal, and transmits the RF signal as an electric wave through an antenna 42 .

The receiver 45 includes an RF receiver 61 which down-converts an RF signal received through the antenna 42 to a BB signal, a BB receiver 62 which demodulates the BB signal and a MAC receiver 63 which subjects the demodulated data to a reception process relating to MAC layer and outputs the data to the main system 40 through the system IF 43 .

A signal received by the antenna 42 is transmitted by the WUSB device 2 so as to have a directivity to a directional space the WUSB host 3 is located in, and a signal transmitted to the other directional spaces as an interference signal has a level considerably lower than that of a signal to its own station. Therefore, the WUSB host 3 does not need an interference wave removal process at the receiving side.

The MAC transmitters 20 a to 20 d and the MAC receiver 33 of the WUSB device 2 , and the MAC transmitter 50 and the MAC receiver 63 of each of the WUSB hosts 3 a to 3 c will specifically be explained.

The MAC transmitters 20 a to 20 d and the MAC receiver 33 of the WUSB device 2 , and the MAC transmitter 50 and the MAC receiver 63 of each of the WUSB hosts 3 a to 3 c perform transmission and reception process relating to MAC layer substantially according to WUSB standard using WiMedia standard (WiMedia Alliance, “MAC Specification: RELEASE 1.5”, [online], Dec. 1, 2009, [searched on Jun. 23, 2010], internet <URL: http://www.wimedia.org/imwp/download.asp?ContentID=16552>).

In WiMedia standard, every station (WUSB device 2 and WUSB hosts 3 a to 3 c ) of every super frame having a cycle of 65,536 μs, formed of 256 media access slots (MAS) having a 256 μs period transmits and receives a beacon to and from each other in a beacon period at the head of the frame to synchronize time of system. Every station adjusts and reserves MAS with beacon and transmits and receives data to and from the other stations with time-division using a reserved MAS period.

A protocol which reserves MAS is called DRP (Distributed Reservation Protocol). The beacon signal includes MAS reservation request, response information (DRP IE) and present reservation status information (DRP Availability IE). Every station can always grasp the reservation status of 256 MAS with information included in the beacon signal.

In the WUSB standard, the WUSB host transmits a management frame called MMC (Micro-scheduled management Command) to a WUSB device to be controlled, and each WUSB device transmits and receives data and communication response packet to and from the WUSB host at a time designated by the MMC transmitted from the WUSB host.

Therefore, the WUSB standard using the WiMedia standard reserves MAS which is a data transmission period of the WUSB host and MAS which is a data transmission period of the WUSB device according to DRP, and transmits and receives data with the reserved MAS.

The MAC transmitters 20 a to 20 d of the WUSB device 2 reserve MAS which is a date transmission period according to DRP as the MAC transmitter 50 of the WUSB hosts 3 a to 3 c to transmit data in the same period through SDMA communication, and transmits data with the reserved MAS.

The MAC receiver 63 of each of the WUSB hosts 3 a to 3 c , monitors MAS data reserved by MAC transmitters 20 a to 20 d of the WUSB device 2 , and when the MAC receiver 63 detects data addressed thereto, it subjects the data to a reception process relating to MAC layer.

An operation example of the thus wireless access system 1 will be explained, referring to FIGS. 4 and 5 .

In FIG. 4 , first, the WUSB host 3 a transmits data, next, the WUSB host 3 b transmits date, and the WUSB device 2 having received the data returns a response signal (ACK) through SDMA communication.

In FIG. 4 , in one super frame of the WiMedia standard, DRP-A represents at least one MAS reserved by the MAC transmitter 50 of the WUSB host 3 a , DRP-B represents at least one MAS reserved by the MAC transmitter 50 of the WUSB host 3 b , and DRP-Dev represents at least one MAS reserved by the MAC transmitters 20 a to 20 d of the WUSB device 2 .

First, in DRP-A, the MAC transmitter 50 of the WUSB host 3 a transmits MMC (MMC-A in FIG.) including data transmission time, ACK transmission request time of the data and next MMC transmission time, and the WUSB device 2 receives this (STEP S 1 ). The MAC transmitter 50 of the WUSB host 3 a designates time in DRP-Dev as the ACK transmission request time.

At the data transmission time designated by MMC, the MAC transmitter 50 of the WUSB host 3 a transmits data (Date Out-A in FIG.), and the WUSB device 2 receives this STEP S 2 ).

Next, in DRP-B, the MAC transmitter 50 of the WUSB host 3 b transmits MMC (MMC-B in FIG.) including data transmission time, ACK transmission request time of the data and next MMC transmission time, and the WUSB device 2 receives this (STEP S 3 ). The MAC transmitter 50 of the WUSB host 3 b designates time in DRP-Dev as the ACK transmission request time.

At the data transmission time designated by MMC, the MAC transmitter 50 of the WUSB host 3 b transmits data (Date Out-B in FIG.), and the WUSB device 2 receives this STEP S 4 ).

Next, in DRP-Dev, at the ACK transmission request time designated by each MMC, the MAC transmitters 20 a to 20 b of the WUSB device 2 corresponding to the directional spaces 4 a and 4 b where the WUSB hosts 3 a and 3 b are located start transmitting ACK or NACK relative to the reception result of each data, and the WUSB hosts 3 a and 3 b receive ACK addressed thereto (STEP S 5 ).

Each signal which represents ACK transmitted from the MAC transmitters 20 a and 20 b of the WUSB device 2 is transmitted to the directional spaces 4 a and 4 b by the SDMA transmitter 22 through the antenna elements 23 a and 23 c.

FIG. 5 represents an example where the WUSB host 3 b requests for data first, the WUSB host 3 a requests for data, the WUSB device 2 transmits the requested data through SDMA communication, and the WUSB hosts 3 a and 3 b return ACK relative to the data they received.

In FIG. 5 , in a super frame in the WiMedia standard, DRP-A represents at least one MAS reserved by the MAC transmitter 50 of the WUSB host 3 a , DRP-B represents at least one MAS reserved by the MAC transmitter 50 of the WUSB host 3 b , and DRP-Dev represents at least one MAS reserved by the MAC transmitters 20 a to 20 d of the WUSB device 2 .

First, in DRP-B, the MAC transmitter 50 of the WUSB host 3 b transmits MMC (MMC-B in FIG.) including data transmission request time and next MMC transmission time including ACK relative to the data, and the WUSB device 2 receives this (STEP S 11 ). The MAC transmitter 50 of the WUSB host 3 b designates time in DRP-Dev as the data transmission request time.

Next, in DRP-A, the MAC transmitter 50 of the WUSB host 3 a transmits MMC (MMC-A in FIG.) including data transmission request time and next MMC transmission time including ACK relative to the data, and the WUSB device 2 receives this (STEP S 12 ). The MAC transmitter 50 of the WUSB host 3 a designates time in DRP-Dev as the data transmission request time.

Next, in DRP-Dev, at the data transmission request time designated by each MMC, the MAC transmitters 20 a to 20 b of the WUSB device 2 corresponding to the directional spaces 4 a and 4 b where the WUSB hosts 3 a and 3 b are located start transmitting each data (Data In-A and Data In-B in FIG.), and the WUSB hosts 3 a and 3 b receive ACK addressed thereto (STEP S 13 ).

Each signal which represents data transmitted from the MAC transmitters 20 a and 20 b of the WUSB device 2 is transmitted to the directional spaces 4 a and 4 b by the SDMA transmitter 22 through the antenna elements 23 a and 23 c.

Next, in DRP-B, at the next MMC transmission time designated by MMC-B, the MAC transmitters 50 of the WUSB host 3 b transmits MMC (MMC-B (ACK) in FIG.) including ACK or NACK response showing data reception results from the WUSB device (STEP S 14 ).

Next, in DRP-A, at the next MMC transmission time designated by MMC-A, the MAC transmitters 50 of the WUSB host 3 a transmits MMC (MMC-A (ACK) in FIG.) including ACK or NACK response showing data reception results from the WUSB device (STEP S 15 ).

As explained above, the wireless access system 1 of the present invention transmits data from the WUSB device 2 to the WUSB hosts 3 a to 3 c through SDMA communication in upbound transmission and from the WUSB hosts 3 a to 3 c to the WUSB device 2 through TDMA communication in downbound transmission. Therefore, in multiple wireless communication between the plural WUSB hosts 3 a to 3 c and the WUSB device 2 , interference between wireless signals from the WUSB hosts 3 a to 3 c is prevented and interference wave removal process in the WUSB device 2 is not needed.

The wireless access system 1 of the present invention conjugately controls the plural WUSB hosts 3 a to 3 c and one WUSB device 2 using time division. Plural WUSB hosts can conjugately use a WUSB device, which is difficult for conventional WUSB standard (“Wireless Universal Serial Bus Specification Revision 1.0”, [online], May 12, 2005, [searched on Jun. 23, 2010], internet <URL:http://www.usb.org/developers/wusb/wusb — 2007 — 0214.zip>).

The wireless access system 1 of the present invention connects the WUSB device 2 such as printers, combined machines and projectors to the plural WUSB hosts 3 a to 3 c such as personal computers at the same time so that they can conjugately use the WUSB device 2 .

An example in which the wireless access system 1 of the present invention performs time-division duplex communication between the WUSB device 2 and the WUSB hosts 3 a to 3 c according to WiMedia standard has been explained. In the present invention, the wireless access system may perform time-division duplex communication between the WUSB device 2 and the WUSB hosts 3 a to 3 c using PCF (Point Coordination Function) control of WLAN (Wireless Local Area Network).

An example in which communication between the WUSB device 2 and the WUSB hosts 3 a to 3 c is made by time-division duplex communication has been explained, and in the present invention, the wireless access system of the present invention may perform frequency-division duplex communication between the WUSB device 2 and the WUSB hosts 3 a to 3 c.

Additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced other than as specifically described herein.

This document claims priority and contains subject matter related to Japanese Patent Application No. 2010-157591 filed on Jul. 12, 2010, the entire contents of which are herein incorporated by reference.