KR100846727B1 - Enhanced ieee 802.15.3 mac protocol for efficient support of sops based on mc-cdma uwb system - Google Patents

Abstract

A method for mitigating IPI simultaneously operating in an MC-CDMA UWB system is provided to restrict the number of links simultaneously operated in a duplicate piconet to two links, thereby removing interference between the overlapped piconets and increasing a restricted throughput. A method for mitigating IPI(Inter Piconet Interference) simultaneously operated in an MC-CDMA(Multi-Carrier Code Division Multiple Access) UWB(Ultra WideBand) system comprises the following steps of: checking whether piconets are overlapped with each other(S100); reconfiguring superframe information so as for only two links belonging to different piconets to be simultaneously operated in the overlapped piconets(S200); and broadcasting a beacon signal including the superframe information in a piconet coordinator(S300).

Description

Interference mitigation method between piconets operating simultaneously in MC-CDMAA based PCS {{Enhanced IEEE 802.15.3 MAC Protocol for Efficient Support of SOPs based on MC-CDMA UWB System}

1 is a diagram illustrating a configuration illustrating a superframe of IEEE 802.15.3.

FIG. 2 is a diagram illustrating a superframe of a method of configuring a piconet in a parent / child or parent / neighbor method.

3 is a flowchart illustrating a method for mitigating interference between piconets operating simultaneously in an MC-CDMA based UWB system according to the present invention;

4 is a view illustrating two piconets overlapping;

5 to 6 are flowcharts illustrating a first embodiment of an interference mitigation method between piconets according to the present invention when two piconets overlap;

7 is a diagram illustrating an example of a configuration of a superframe according to the first embodiment of the present invention;

8 is a view illustrating three piconets overlapping each other;

9 to 10 are flowcharts illustrating a second embodiment of an interference mitigation method between piconets according to the present invention when three piconets overlap.

11 is a diagram showing an example of the configuration of a superframe according to a second embodiment of the present invention;

The present invention relates to a method for removing interference between piconets, and more particularly, to a method for removing interference and increasing throughput between piconets having overlapping areas.

Ultra wideband (UWB), a next-generation wireless communication technology, is a wireless technology for transmitting a large amount of digital data through a wide spectrum frequency at low power. The standardization of UWB is IEEE 802.15.3. In other words, a working group for establishing a wireless PAN standard is in progress. IEEE 802.15.3. High-Rate WPAN technology developed by Working Group refers to a communication protocol that supports high-speed multimedia transmission between wireless devices at short range.

The IEEE 802.15.3 MAC protocol is designed to support high-rate wireless personal area networks (WPANs) at low power, and is an ad hoc network called a piconet around a piconet coordinator (PNC). It operates on the principle of Time Division Multiple Access (TDMA) within one piconet for interference-free connection between devices (hereinafter, referred to as 'DEV').

The MC-CDMA method is a multiple access method based on an OFDM system, and can manage a plurality of users (users) by simultaneously spreading frequency bands and allocating different frequency bands. In MC-CDMA, frequency domain spreading is applied. At the transmitting side, each user generates N data symbols during an OFDM symbol period and multiplies a spreading code. Combine all user symbols at the same time and send. Each user's data symbol is a method of obtaining data after despreading FFT (Fast Fourier Transform) output.

1 is a diagram illustrating a configuration illustrating a superframe of IEEE 802.15.3. Referring to FIG. 1, the m-th superframe includes a beacon, a contention access period (hereinafter referred to as 'CAP'), and a channel time allocation period (hereinafter referred to as 'CTAP'). .

At the beginning of every superframe, the PNC sends a beacon that provides piconet timing information, and the CAP controls how data is accessed simultaneously and asynchronously.

CTAP consists of Channel Time Allocation (CTA) and Management CTA (MCTA), and CTA is used to connect simultaneous or asynchronous data communication according to the access method controlled by CAP. Used for communication between PNCs.

When the source DEV communicates with the destination DEV, the source DEV that wants to communicate transmits a Channel Time Request (hereinafter, 'CTRq') to the PNC. Here, the PNC allocates new CTAs for connection with a destination DEV, and all CTA information including a start time and a period are put in a beacon and transmitted to the PNC. This is called the “beacon signal,” and according to the transmitted beacon signal, all connections operate during their CTA without any interference.

On the other hand, if different piconets are separated by a considerable distance from one or more piconets at the same time, Inter Piconet Interference (hereinafter, referred to as 'IPI') does not occur. Occurs.

In general, a method of constructing a piconet in a parent / child or parent / neighbor manner has been used to solve such a problem.

FIG. 2 is a block diagram illustrating a superframe of a method of configuring a piconet in a parent / child or parent / neighbor method.

Referring to FIG. 2, a method of configuring a piconet as a parent / child or a parent / neighbor, when the PNC detects the presence of another piconet, the PNC detects the piconet and the parent. By forming a / child or parent / neighbor relationship, a parent piconet can have one or more dependent piconets, ie, child or neighbor piconets. At this time, the data transmission of the child piconet and NAVER piconet is present in the private CTA of the parent piconet.

The child or neighbor piconet superframe is in Private-CTA2 of the parent piconet, as shown in FIG. However, the above-described method has a problem in that throughput of the piconet is limited because the DEVs of the parent piconet cannot communicate while the child superframe and the neighbor superframe are in operation.

The present invention has been made to solve the above problems of the prior art, and an object of the present invention is to provide a method for mitigating interference between piconets so that overlapping piconets operate simultaneously without interference in an MC-CDMA based UWB system.

In order to solve the above problems, an interference mitigation method between piconets operating simultaneously in an MC-CDMA based UWB system according to the present invention is a method for mitigating interference between piconets formed by a piconet coordinator and a plurality of devices and intermediary devices. A first step of checking whether the overlapped piconet is a second step of reconstructing superframe information such that only two links belonging to different piconets in the overlapped piconet are simultaneously operated, and the piconet coordinator broadcasts the beacon signal containing the superframe information It comprises a third step.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

3 is a flowchart illustrating an interference mitigation method between piconets operating simultaneously in an MC-CDMA based UWB system according to the present invention.

Referring to FIG. 3, the present invention relates to a method of using two limited links in an overlapped piconet and assigning a different spreading matrix to the limited links of the piconet. In step 1 (S100), the number of piconets that can be operated simultaneously during each CTA is limited to two links belonging to different piconets so that separate piconets can operate simultaneously without interference. A second step of allocating a spreading matrix (S200), and after the process of reallocating a superframe, the senior piconet coordinator (Senior PNC) includes a third step (S300) of transmitting a beacon signal containing the reallocated superframe information. It is done by In the MC-CDMA UWB system of the above process, one symbol is transmitted twice, and when a signal is detected by the receiver, a joint minimum mean square error (MMSE) measurement method may be adopted.

Specifically, first, check whether the piconets overlap, and then identify the links generated by the devices wishing to communicate.

The senior piconet coordinator is selected from the multiple piconet coordinators of the nested piconets. Here, one example of the method of selecting the senior piconet coordinator is to select a piconet coordinator including the most intermediate devices (IDEV, Intermediate DEV) existing in each overlapping region as the senior coordinator.

The intermediary device IDEV is a device existing in the overlapped area, and at least one intermediary device exists in the overlapped area.

The intermediary device receives beacon signals from at least two piconets. A device included in each piconet may select an intermediary device by checking whether a beacon signal is received from at least two piconets as described above.

When a senior piconet coordinator is selected, the senior piconet coordinator creates a group of two links and assigns them to each CTA of the superframe when multiple devices simultaneously want to communicate, but two links assigned to each CTA are different from each other. Must be a link to That is, only one link in one piconet communicates during one CTA. However, the maximum communicable link during a CTA is limited to two of all overlapping piconets.

In addition, in order to minimize interference of two links allocated to each channel time allocation (CTA), the spreading codes are multiplied by the spreading codes using spreading matrices having different spreading codes.

Table 1 shows an example of a spreading matrix having different spreading codes to be applied to two limited links.

Spreading code Diffusion Matrix 1 One One One One One One One One One -One One -One One -One One -One One One -One -One One One -One -One One -One -One One One -One -One One Diffusion matrix 2 One One One One -One -One -One -One One -One One -One -One One -One One One One -One -One -One -One One One One -One -One One -One One One -One

 The interference mitigation method between piconets operating simultaneously in the MC-CDMA based UWB system according to the present invention is not limited to the spreading codes shown in Table 1 above.

Looking at the configuration of the super frame used in the present invention.

The superframe includes a beacon, a contention access period (hereinafter referred to as "CAP"), and a channel time allocation location (hereinafter referred to as "CTAP"). In the beacon area of the superframe, beacons with timing information of each overlapping piconet are sequentially allocated to the slots. If two piconets overlap, beacon 1 and beacon 2 are sequentially assigned to slots, and if three piconets overlap, beacon 1, beacon 2, and beacon 3 are allocated to slots.

CTAP consists of Channel Time Allocation (CTA) and Management CTA (MCTA), and CTA is used to connect simultaneous or asynchronous data communication according to the access method controlled by CAP. Used for communication between PNCs.

Each of the above-mentioned CTAs is assigned two link groups. That is, only two links communicate with each CTA, and the two links operate on different piconets and operate without interference.

Finally, the senior piconet coordinator broadcasts the beacon signal having the superframe information to devices belonging to its own piconet. Among the devices receiving the beacon signal, the intermediary device transmits it to the surrounding normal piconet coordinator, and the normal piconet coordinator broadcasts it to devices belonging to its own piconet.

According to the superframe information, the links of the corresponding piconets operate in the corresponding CTA.

Hereinafter, a case in which two piconets overlap with each other according to the first embodiment of the present invention will be described.

4 is a diagram illustrating two piconets overlapped. The case in which two piconets overlap with each other will be described in detail with reference to FIG. 4. Piconets 1 and 2 having PNC-1 and PNC-2 are present in an overlapped state, and each piconet has a piconet having a senior piconet coordinator (Senior PNC). Divide into piconets with normal piconet coordinator (Normal PNC).

In more detail, the device DEV indicated by a circle is a device included in Piconet 1, and the device DEV indicated by a rectangle is a device included in Piconet 2. Intermediate DEVs of the overlapped regions are indicated by black circles, and the piconet coordinator (PNC) is positioned at the center of each piconet.

If the device of each piconet wants to communicate, L-1 and L-2 may be generated in the link connecting the source and the destination, respectively. In this case, in FIG. 3, two overlapping piconets have links L-1 and L-2 that can operate simultaneously.

5 to 6 are flowcharts illustrating a first embodiment of an interference mitigation method between piconets according to the present invention when two piconets overlap as described above. First, referring to FIG. 5, it is checked whether piconets exist in an overlapping state in a first step (S110). Various devices DEVs existing in the overlapped piconets receive a beacon signal from the piconets (S120). The device DEV receiving the beacon signal checks whether another beacon signal is received (S130), and when the device DEV receives another beacon signal, the device becomes the intermediary device IDEV, and the overlapped piconet Capacity is examined to distinguish between piconets having a senior piconet coordinator (senior PNC) and piconets having a normal piconet coordinator (normal PNC) (S140). The piconet coordinator (PNC) having the highest capacity is selected as the senior piconet coordinator (senior PNC) (S150). DEV not receiving the beacon signal may receive a beacon signal including the superframe adjustment information from the PNC of its area (S160).

Referring to FIG. 6, beacon 1 and beacon 2 are allocated to different slots in a superframe of the piconet for the operation of two limited links in the two piconets overlapping in the second step (S210). The number of links of piconets that can operate simultaneously to each CTA is limited to two, and the links are evenly distributed to the overlapping piconets to allocate two restricted links to each CTA (S220). In order to minimize interference of two limited links allocated to each CTA, different spreading codes are multiplied with each link by using different spreading matrices (S230).

7 is a diagram illustrating an example of a configuration of a superframe according to the first embodiment of the present invention. In the above description, it can be seen from FIG. 7 that the location of the beacon signal and the link operating in each CTA are limited to two in the superframe.

Next, a case in which three piconets overlap with the second embodiment of the present invention will be described.

FIG. 8 is a view illustrating three piconets overlapping, and FIGS. 9 to 10 are flowcharts illustrating a second embodiment of an interference mitigation method between piconets according to the present invention when three piconets overlap. The same method works when three or more piconets overlap.

8 and 9 to 10, when three piconets overlap, the first piconets 1 and 2, 3 exist in an overlapped state (S410). DEV-A and DEV-B present in the overlapped piconet region receive beacon signals from PNC-2 and PNC-3, respectively, including request information for CTAs of devices DEVs of piconet 2 and 3 (S420). ). The DEV-A and DEV-B operate as an intermediate device (IDEV) (S430), and transmit a signal containing a request information signal for CTAs to the PNC-1 (S440). The PNC-1 stores the CTAs request and adjusts superframe information according to the request (S450). The senior piconet coordinator here is PNC-1.

Referring to the first step in the case where the three piconets are superimposed by using the example of the three piconets in Fig. 8 as shown in the piconet 1,2,3 having PNC-1 and PNC-2 PNC-3 There are overlapping links and each piconet has links that can operate according to the proposed method. Here, Piconet 1 operates as a piconet with a senior piconet coordinator (Senior PNC) because IDEV-A and IDEV-B have two IDEVs (the PNC of the piconet having the largest number of nested piconets is designated as senior PNC). do.

In the second step, beacon 1, beacon 2, and beacon 3 are allocated to different slots in the superframes of the divided piconets so as to operate simultaneously without interference (S510). The number of piconets that can operate simultaneously in each CTA is limited to two (S520), and each piconet distributes the links that can operate simultaneously to the piconets equally so that two links that operate simultaneously in each CTA The operation of assigning is performed (S530). In order to minimize interference of two limited links allocated to each CTA, each link is multiplied by a different spreading code using the spreading matrix given in Table 1 (S540).

11 is a diagram illustrating an example of a configuration of a superframe according to a second embodiment of the present invention. Referring to the above description in detail with reference to FIG. In addition, the number of available code streams is changed according to the channel state of the link to improve the yield success rate and increase the link success probability. For example, if the channel state is good, four code streams are used. If the channel state is bad, one code stream is used.

In the third step, when the process of reallocating the superframe is finished, the senior piconet coordinator (senior PNC) transmits a beacon signal containing the reallocated superframe information.

That is, finally, the senior piconet coordinator broadcasts the beacon signal having the above superframe information to devices belonging to its own piconet. Among the devices receiving the beacon signal, the intermediary device transmits it to the surrounding normal piconet coordinator, and the normal piconet coordinator broadcasts it to devices belonging to its own piconet.

According to the superframe information, the links of the corresponding piconets operate in the corresponding CTA.

The present invention described above has proposed a method for removing interference of piconets using intelligent channel time allocation, which eliminates interference caused by overlapping two piconets, and allows two links limited to overlapped piconets to operate smoothly. Has

As described above and described with reference to a preferred embodiment for illustrating the technical idea of the present invention, the present invention is not limited to the configuration and operation as shown and described as described above, it is a deviation from the scope of the technical idea It will be understood by those skilled in the art that many modifications and variations can be made to the invention without departing from the scope of the invention. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

The interference mitigation method between piconets operating simultaneously in the MC-CDMA based UWB system according to the present invention configured as described above is based on the number of links simultaneously operating in the MC-CDMA (multi-carrier-code division multiple access) scheme and the overlapped piconets. By using the two-limiting method, it is possible to remove interference from overlapping piconets and increase the limited throughput.

Claims (5)

In the interference mitigation method between the piconet coordinator and the piconet formed by a plurality of devices and intermediary devices, A first step of checking whether the piconets overlap; Reconstructing superframe information such that only two links belonging to different piconets operate simultaneously in the overlapped piconets; And The piconet coordinator comprises a third step of broadcasting a beacon signal containing the superframe information, The first step may include a first step of checking whether two arbitrary piconets overlap each other; And Interference mitigation between piconets operating simultaneously in the MC-CDMA based UWB system including a second process of selecting one of the overlapped piconet piconet coordinators as a senior piconet coordinator and selecting the remaining piconet coordinators as normal piconet coordinators Way. delete The method according to claim 1, The second process is a method for mitigating interference between piconets operating simultaneously in a MC-CDMA based UWB system, characterized in that the piconet coordinator that accommodates the intermediary device among the overlapped piconets is selected as the senior piconet coordinator. The method according to claim 1, The second step may include allocating a plurality of beacons including timing information of each piconet to different slots in the superframe information; Limit the number of links of piconets that can operate simultaneously to each channel time allocation (CTA) of the superframe, and distribute the links evenly to the overlapping piconets so that the two limited link links are assigned to each channel time allocation (CTA). The process of assigning a dog; and MC-CDMA including multiplying the two spreading code by using the spreading matrix having different spreading codes to minimize the interference of the two links allocated to each channel time allocation (CTA) Interference mitigation method between piconets operating simultaneously in base UWB system. The method according to claim 1, The third step may include: propagating, by the senior piconet coordinator, the beacon signal to devices in a corresponding piconet including the intermediary device; Receiving, by the intermediary device present in the overlapped area, the beacon signal and transmitting the normal beacon coordinator; and The normal piconet coordinator is a method for mitigating interference between piconets simultaneously operating in the MC-CDMA based UWB system comprising the step of propagating the beacon signal to the devices included in its piconet.

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