KR20130005189A - Method and apparatus for accessing channel in wireless body area network - Google Patents

Abstract

The present invention proposes a method and apparatus in which a plurality of peripheral devices or sensors are connected to a short range communication system in a short range communication system. In addition, the present invention is particularly suitable for a near field communication environment, such as around the human body or inside the human body, and proposed for a mesh network communication environment in which one piconet centered on the human body is formed or connected to a plurality of devices. do. Meanwhile, in the communication access method, a method of performing distributed synchronization without using a centralized synchronization method and efficient distributed resource connection is proposed. By the effect of this method, the transmission rate can be improved and the transmission delay can be reduced.

Description

Efficient resource access method and apparatus in JANN {METHOD AND APPARATUS FOR ACCESSING CHANNEL IN WIRELESS BODY AREA NETWORK}

The present invention relates to a wireless body area network (WBAN), and more particularly, to a method and apparatus for network terminals constituting a WBAN in a WBAN to be distributed in synchronization and to access resources in a distributed manner.

WBAN is standardized under the international standard of IEEE 802.15.6 TG6 BAN.WBAN is capable of providing medical services such as telemedicine and wearable computing through a communication network around 3 meters. To provide entertainment services using wearable equipment or motion sensors. In addition, a similar standard is in progress as an international standard called IEEE 802.15.4j MBAN (Medical BAN), and 802.15.4j is an amendment for using existing 802.15.4 in the MBANS (Medical BAN Service) band of 2.36 ~ 2.4GHz. ) It is prescribed by standard.

As shown in FIG. 1, a WBAN is a type of personal area network (PAN) including a plurality of network terminal devices, and the network terminal device may be classified into a coordinator and a plurality of network devices. In this case, the coordinator may be, for example, a portable terminal such as a PDA, a mobile phone, or a smartphone, and the network device may be various kinds of sensors and devices attached to the body.

When multiple network devices are connected to one coordinator, it is called a star topology, and when a coordinator and multiple network devices are connected to each other, it is called a peer-to-peer topology. In general, a star topology is often used for services that collect information around users. In FIG. 1, a full function device refers to a terminal capable of both a coordinator and a network device, and a reduced function device refers to a terminal that does not serve as a coordinator.

The main application of WBAN is to collect biometric information from medical sensors and send it to medical institutions. The coordinator responds to the server of the medical institution by wire or other wireless communication, and sends the data received from the device such as a sensor connected to the WBAN to the medical institution server.

In such a WBAN healthcare system, mainly targeting devices having a small size, such as a sensor with poor power conditions, and a mobile power source such as a battery, it is the most important system requirements to minimize the power consumption. To reduce power consumption, there are ways to reduce activity intervals, such as low duty cycling and increasing protocol efficiency.

In the short-range communication system, a carrier sensing multiple access-collision avoidance (CSMA-CA) scheme is mainly applied to relatively easily handle resource access control and interference control. When multiple personal area networks (PANs) composed of star topologies exist in the same area with interference, in order to use the time division multiple access (TDMA) method, coordinators of each PAN exchange information to each other and thus overlap each other. Adjustments should be made to avoid This operation is typically performed at the MAC or network layer. However, due to the high complexity, in practice, the CSMA-CA scheme is widely used, and this interference problem between PANs is easily solved.

The CSMA-CA scheme is also easily applied to peer-to-peer topologies with more complex connection characteristics than star topologies. However, the CSMA-CA scheme is less efficient in utilizing resources than the TDMA scheme. In general, we expect 40 ~ 60% of data rate compared to TDMA. Since the efficiency of resource connection is low, it takes longer time to send the same amount of packets, thus consuming more power. Therefore, various protocol designs have been studied to improve the operation of the inefficient CSMA-CA scheme.

2 and 3 show communication operations in a beacon-enabled PAN (BPAN) and a non-beacon-enabled PAN (NBPAN), respectively. Referring to FIG. 2, in the BPAN, network terminals (coordinator 10 and network device 30) perform synchronization with a reference time through reception of a beacon frame (step 31), and competition of a superframe indicated in the beacon frame. At the start of the interval, a slotted CSMA-CA operation may be performed from a backoff slot boundary calculated according to the reference time (steps 33 and 35).

On the other hand, referring to Figure 3, NBPAN does not inform the reference time for forming a superframe, so it operates as an unslotted CSMA-CA (steps 41 and 43).

4 is a diagram illustrating a transmission success rate 50 of the slot CSMA-CA scheme and a transmission success rate 60 of the non-slot CSMA-CA scheme. Referring to FIG. 4, although it depends on propagation delay, non-slot CSMA-CA generally decreases the transmission success rate as the amount of packets to be transmitted increases. However, nonslot CSMA-CA is sometimes better in terms of transmission delay and collision.

In nonbeacon enabled PAN (NBPAN), a network device sends a poll frame to a coordinator in order to synchronize between two terminal devices, for example, a coordinator and a network device, or the coordinator sends a beacon frame to a network device. Send data to the server to check if there is any data to send and perform packet transmission. The beacon frame sent by the coordinator in NBPAN is set to macBeaconOrder = 15, indicating that it will not form a superframe. In BPAN, macBeaconOrder is set smaller than 15 and sent.

As described above, in NBPAN, two network terminals wishing to perform communication need to synchronize by sending a beacon or poll frame every time data is transmitted, and always listen in an active state to receive such beacon or poll frame. This is a poor implementation because it has a disadvantage of listening.

In general, the operation according to the CSMA-CA method, a network terminal having data waits for a certain time through a backoff process to avoid a collision without transmitting data immediately, and then senses a channel (Clear Channel Assessment, CCA). If it is determined that it is idle, transmission starts. This resource access method is mainly used in the contention period.

5A and 5B illustrate a conventional CSMA-CA scheme, and in particular, illustrates a CSMA-CA algorithm applied to IEEE 802.15.4. In FIG. 5A, step 101 is a step of checking whether the WBAN uses a slot CSMA-CA scheme or a non-slot CSMA-CA scheme. Steps 103 to 125 show a process of operating the network terminal according to the slot CSMA-CA scheme, and steps 131 to 141 show a process of operating according to the non-slot CSMA-CA scheme.

There are three main variables in this CSMA-CA algorithm: NB, CW, and BE. The NB corresponds to the number of retries due to backoff in one connection attempt. CW is the number of backoff intervals needed to determine if the channel is idle. 5A and 5B, CW starts at 2 and decreases by 1 every time the backoff is performed. If the channel is idle until 0, packet transmission is performed. BE is related to the number of backoff intervals that the device must wait before performing channel sensing (CCA), and operates by selecting any number from 0 to 2 ^BE -1 in FIGS. 5A and 5B. If channel sensing (CCA) is used and another device is in use, the BE increases by one, and the random number to wait for is determined in twice the range.

The conventional CSMA-CA scheme does not perform the constant physical carrier sensing performed by reducing the backoff counter in order to increase energy efficiency. As the BE is increased every time the channel is found to be busy, it operates in a more conservative resource access method than the CSMA-CA method in which the BE is increased only when a collision occurs. Because of this conservative nature of resource access, the backoff time for successful transmission is long and throughput is degraded.

Therefore, if the transmission attempt of the device can be distributed to different time intervals, it is possible to reduce the phenomenon of frequent backoff by channel sensing in the CSMA-CA scheme.

The present invention provides a method and apparatus for achieving distributed synchronization between devices in a WBAN and controlling distributed resource access to be efficiently performed based on this.

In addition, the present invention provides a method and apparatus for achieving distributed synchronization between devices in a WBAN and minimizing collision in a contention access period based on the distributed synchronization.

In addition, the present invention proposes a method and apparatus for distributed control so that devices occupy different resources so as to reduce delay due to backoff while using CSMA-CA scheme in a WBAN formed of NBPAN.

In the present invention, at least one network terminal device included in a wireless body area network (WBAN) includes a first oscillator operating at a period T and whose phase increases in proportion to time, wherein the phase has a threshold phase value. When the first synchronization signal is reached, and when the first synchronization signal is received from the outside, PCO anti-phase synchronization with respect to the oscillator by performing phase adjustment of the oscillator according to the reception time of the received first synchronization signal And determining at least some of the resource access intervals of the resource access intervals calculated using the first phase controller, the transmission time of the transmitted first synchronization signal, and the reception timing, as the final resource access interval, and the oscillator of the oscillator. Determine a start time of the last resource access section so that phase adjustment may be made within the last resource access section; It includes a controller for transmitting data by attempting a resource connection during the last resource access interval.

In addition, the present invention provides a method for accessing at least one network terminal device included in a wireless body area network (WBAN), the phase controller including a first oscillator operating at a period T and whose phase increases in proportion to time. When the phase reaches a threshold phase value by using the first synchronization signal is sent, when receiving the first synchronization signal from the outside, by adjusting the phase of the oscillator according to the reception time of the received first synchronization signal Performing a PCO anti-phase synchronization with respect to the oscillator, determining at least some of the resource access intervals of the resource access intervals calculated using the transmission time of the transmitted first synchronization signal and the reception time as the final resource access interval. And the last step of adjusting the phase of the oscillator within the final resource access section. The process of determining the start point of the source access period and includes the step of transmitting the data by attempting to access resources over the last resource access period.

The present invention achieves distributed synchronization among devices in the WBAN, and can control the distributed resource access efficiently based on this. In addition, the present invention achieves distributed synchronization among devices in a WBAN, and can minimize collisions in a contention access period based on this. In addition, the present invention can be distributedly controlled so that the devices occupy different resources so as to reduce the delay due to the backoff while using the CSMA-CA method in the WBAN formed of the NBPAN.

1 is a diagram illustrating an example topology of a WBAN;
2 is a diagram illustrating a communication operation of a network terminal in a BPAN;
3 is a diagram illustrating a communication operation of a network terminal in NBPAN;
4 is a diagram illustrating a transmission success rate of a slot CSMA-CA scheme and a transmission success rate of a non-slot CSMA-CA scheme;
5A and 5B show a conventional CSMA-CA algorithm,
6 is a diagram illustrating a PCO in-phase synchronization process;
7 is a diagram illustrating a PCO anti-phase synchronization process;
8 is a diagram illustrating an oscillator operation example of a device;
9 is a view illustrating an operation process of a network terminal for PCO phase synchronization;
10 and 11 illustrate an operation process of a network terminal for PCO antiphase synchronization;
12 to 14 are diagrams showing an application example of a distributed non-slot CSMA-CA scheme for NBPAN according to an embodiment of the present invention;
15 and 16 illustrate an operation of a network terminal for implementing a distributed non-slot CSMA-CA scheme for NBPAN according to an embodiment of the present invention;
17 and 18 illustrate the configuration of a network terminal according to an embodiment of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the same components in the drawings are represented by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In the following description, a wireless body area network (WBAN) is a type of personal area network (PAN) including a plurality of network terminal devices, and the network terminal device may be divided into a coordinator and a plurality of network devices. Can be. In this case, the coordinator may be, for example, a portable terminal such as a PDA, a cellular phone, or a smartphone, and the network device may be, for example, various kinds of sensors and devices attached to the body.

The present invention relates to a method of controlling a network terminal constituting a WBAN in a non-beacon-enabled WBAN, that is, a non-beacon-enabled PAN (NBPAN), so that time intervals for accessing a channel for communication with each other overlap at least. In addition, we consider how the network devices can operate as simply and distributedly as possible without the coordinator's control process for such control.

In order to allow network devices to overlap at least the time intervals for accessing channel resources without special control of the coordinator, network terminals exchange information about the time intervals for accessing channel resources, and know each other and use this information. Attempts to access resources in different time intervals will be common. However, it is necessary for network terminals to send additional messages for exchanging information on these time intervals, and it takes a considerable time for all network terminals to fully know each other's information. As such, network changes may not be suitable in dynamic situations, such as when there is user movement.

Therefore, the present invention intends to follow a method of exchanging and operating a signal in a physical layer, rather than a method of exchanging messages in a MAC layer. Pulse-Coupled Oscillator (PCO) Synchronization has been studied as an algorithm related to this type of synchronization. PCO synchronization is a phenomenon known in many fields besides communication, and various examples have appeared in chemistry, physics, and biology as a mechanism by which many entities realize synchronization without centralized control.

6 shows In-phase Synchronization operation, which is a general PCO synchronization. Each of Device A, Device B, Device C, Device D, and Device E has an Oscillator with its own phase and firing period of the synchronization signal. At this time, it is assumed that the synchronization function for the period T and phase synchronization of the oscillator provided in each device (A, B, C, D, E) is the same. In FIG. 6, circles in which the devices A, B, C, D, and E are located represent a current phase of each device on a period T, and a fire point represents a timing of firing a synchronization signal in a period T (step 210). .

When the devices A, B, C, D, and E receive a synchronization signal from the outside, the devices A, B, C, D, and E give positive or negative feedback according to the characteristics of the oscillator's synchronization function with respect to the phase (step 220). This operation is repeated several times to complete phase synchronization in which phases between the oscillators of each device are the same (step 230).

A mechanism similar to PCO phase synchronization is shown in FIG. 7 for the operation of PCO anti-phase synchronization. Each of Device A, Device B, Device C, Device D, and Device E has an Oscillator with its own phase and firing period. In this case, it is assumed that the period T and the synchronization function for the antiphase synchronization of the oscillator provided in each of the devices A, B, C, D, and E are the same. In FIG. 7, circles in which the devices A, B, C, D, and E are located represent phases of the devices on a period T, and a fire point represents a timing of firing a synchronization signal in a period T (step 310). When the devices A, B, C, D, and E receive a synchronization signal from the outside, the devices A, B, C, D, and E give a positive or negative feedback with respect to the phase according to the characteristics of the synchronization function of the oscillator (step 320). This operation is repeated several times to complete the anti-phase synchronization in which the offset between phases of the oscillators of the devices A, B, C, D, and E is the same (step 330).

In both of the above schemes, each of the devices A, B, C, D, and E receives a positive or negative feedback with respect to the oscillator's phase when a synchronization signal is externally received. It becomes the output of a specific function, for example, a synchronization function, which takes as input the current phase at the time of receiving the synchronization signal. 8 is a diagram illustrating an operating principle of an oscillator when a device receives a synchronization signal from a neighbor device. In FIG. 8, the phase of the oscillator is denoted by Φ and increases linearly with time t. Since the oscillator's operation is a repetitive rotation, the phase returns to zero again when a certain threshold phase value φ _th is reached. The critical phase value φ _th is often 1, but the case of using a digital counter is also considered here.

Initially, the phase of each oscillator is set to take T time to rotate one turn so that the oscillator has a period T. However, when the synchronization signal is received from the neighboring device at the time t _event , the phase value? _Event at that time becomes the input of the synchronization function F (Φ). The output value F (Φ _event ) thus obtained becomes a phase change amount for phase change, and the phase change amount is added to the current phase value Φ _event . Thus, the final changed phase will be Φ _event + F (Φ _event ). Accordingly, the launch timing of the next sync signal will be faster than the period 2T. This process is repeated every time a synchronization signal is received from the neighboring device, so that the oscillator of the device and the oscillator of the neighboring device are out of phase and emit the synchronization signal at the same time.

The present invention employs this PCO synchronization mechanism to allow synchronization between each network terminal device. In other words, according to the present invention, the network terminal periodically transmits a synchronization signal and, according to the PCO synchronization mechanism, has an oscillator synchronized using the received synchronization signal, so that synchronization is naturally performed at the physical layer. At the same time, the resource access section is determined in consideration of the reception time of the synchronization signal received from the other network terminal and the transmission time of the synchronization signal of the own, and transmits data in the determined resource access section.

An example of the configuration of the network terminal device according to the present invention is illustrated in FIG. 17. Referring to FIG. 17, the network terminal apparatus 1000 includes a controller 1010, a synchronization signal detector 1020, a phase controller 100, a CSMS-CA operation interval calculator 1040, and a synchronization time information memory ( 1050, a synchronization signal transmitter 1025, a modulator 1060, an encoder 1070, a demodulator 1080, a decoder 1090, and a baseband unit 1100.

The controller 1010 controls the overall operation of the network terminal apparatus 1000. According to the present invention, the controller 1010, the CSMS-CA operation interval calculator 1040, the synchronous time information memory 1050, The modulator 1060, the encoder 1070, the demodulator 1080, the decoder 1090, and the baseband unit 1100 are controlled.

The encoder 1070 encodes data under the control of the controller 1010 and outputs the data to the modulator 1060. The modulator 1060 modulates data input from the encoder 170 and outputs the modulated data to the base band unit 1100. The baseband unit 1100 is controlled by the controller 1010. Baseband processing of the data input from the modulator 1060 is transmitted. The baseband unit 1100 outputs data received from the outside to the demodulator 1080, and the demodulator 1080 demodulates the input data to the decoder 1090. The decoder 1090 decodes data input from the demodulator 1080 and transmits the decoded data to the controller 1010.

The sync signal detector 1020 detects that a sync signal received from another network terminal is received through the baseband 1100 and notifies the controller 1010. Accordingly, the controller 1010 notifies the phase controller 1030 that the synchronization signal has been received, and stores the reception time of the synchronization signal in the synchronization time information memory 1050. In addition, the controller 1010 stores the transmission time of the synchronization signal of the network terminal 1000 transmitted by the phase controller 1030 in the synchronization time information memory 1050.

The phase controller 1030 includes the oscillator mentioned in the above description and adjusts the phase of the oscillator in accordance with the PCO synchronization mechanism. The oscillator has a period T, and notifies the sync signal transmitter 1025 when the launch time arrives, whereby the sync signal transmitter 1025 sends a sync signal at that time. The phase controller 1030 notifies the controller 1010 of the launch timing of the synchronization signal.

The PCO synchronization mechanism can be applied to various fields, and there are some parts to be considered when used in communication. First, if the synchronous signal is simply composed of one pulse, it may be difficult to distinguish from other pulses from an external system, which may cause difficulty in synchronizing. For this reason, it is appropriate to use a signal composed of a plurality of pulse trains, such as a preamble or a PN (Pseudo Noise) sequence, which are commonly used in communication, so that it can be distinguished from interference or noise when received. In the present invention, since the PCO phase synchronization and the PCO antiphase synchronization are separately used, two synchronization signals composed of such a plurality of pulse trains are required. Accordingly, the first synchronous signal and the second synchronous signal will be referred to as sync-word or anti-sync word, respectively. The first synchronous signal, i.e., the sync word, is used to perform phase adjustment using the synchronization function F _Sync (Φ) for PCO phase synchronization, and the second synchronous signal, i.e., the anti sync word, is synchronized for PCO antiphase synchronization. Used to perform phase adjustment using the function F _Antisync (Φ).

In order to apply PCO phase synchronization or PCO antiphase synchronization in communication, the operation may be improved by considering propagation delay and the like.

The oscillator, that is, the phase controller 1030, can support only one of the synchronization schemes of the PCO phase synchronization and the PCO antiphase synchronization, and the synchronization function is also one of F _Sync (Φ) and F _Antisync (Φ) according to the supported synchronization scheme. It will support either. Accordingly, the outgoing synchronization signal may also be one of a sync word and an anti-sync word according to the type of the phase controller 1030. Therefore, in the present invention, each network terminal is provided with a phase controller 1030 and a synchronization signal transmitter 1025 of the same type.

9 to 11 illustrate the operation of the network terminal 1000 according to the PCO phase synchronization and the PCO antiphase synchronization according to an embodiment of the present invention.

9 is a diagram illustrating a PCO phase synchronization process when the network terminal 1000 includes a phase controller 1030 that supports PCO phase synchronization. It is assumed that the oscillator included in the phase controller 1030 has a period T, and the phase change amount ΔΦ over time is set for the period T, so that the phase Φ increases by ΔΦ per unit time. In addition, it is assumed that the phase controller 1030 supports a synchronization function F _Sync (Φ) for PCO phase synchronization in which phase adjustment is performed in a negative direction when a sync word is received from another network terminal.

Referring to FIG. 9, the phase controller 1030 increases the phase φ by ΔΦ per time (step 401). In step 403, the phase? Reaches a threshold phase value for inducing the sync word transmission. If the phase is the threshold phase value, the sync word transmitter 1025 determines the sync word transmission time and transmits the sync word through the sync signal transmitter 1025. ). At this time, the information on the time point at which the network terminal 1000 substantially transmits the sync word is stored in the synchronization time information memory 1050 by the controller 1010. The phase value Φ is reset (step 407), and the phase φ is increased by ΔΦ per time (step 401).

If it is detected that the sync word has been received from the outside through the synchronization signal detector 1020 in the state where the current phase Φ does not reach the threshold phase value (step 409), the phase controller 1030 sinks on the period T. The phase value of the oscillator is adjusted by adding the change value calculated by substituting the phase value? Corresponding to the word reception time point to the synchronization function F _Sync (Φ) for PCO phase synchronization to the current phase? Information on the reception time of the sync word is stored in the synchronization time information memory 1050.

According to the result of such adjustment, the sync word is not transmitted regularly at each period T, but is transmitted at the transmission time adjusted in accordance with the timing of receiving the sync word from the neighboring network terminal.

10 is a diagram illustrating a PCO antiphase synchronization process when the network terminal 1000 includes a phase controller 1030 that supports PCO antiphase synchronization. It is assumed that the oscillator included in the phase controller 1030 has a period T, and the phase change amount ΔΦ over time is set for the period T, so that the phase Φ increases by ΔΦ per unit time. In addition, it is assumed that the phase controller 1030 supports a synchronization function F _Antisync (Φ) for PCO anti-phase synchronization, in which phase adjustment is performed in a negative direction when an anti sync word is received from another network terminal.

Referring to FIG. 10, the phase controller 1030 increases the phase Φ by ΔΦ per time (step 501). If the phase Φ reaches a threshold phase value for inducing anti-sync word transmission (step 503), if it reaches the threshold phase value, it is determined as the anti-sync word transmission time point, and the anti-sync word is transmitted through the synchronization signal transmitter 1025. Call (step 505). At this time, the information on the time point at which the network terminal 1000 substantially transmits the anti sync word is stored in the synchronization time information memory 1050. The phase value Φ is reset (step 507) and the phase φ is increased by ΔΦ per time (step 501).

If it is detected that the sync word has been received from the outside through the synchronization signal detector 1020 in the state where the current phase Φ does not reach the threshold phase value (step 509), the phase controller 1030 sinks on the period T. The phase value of the oscillator is adjusted by adding the change value calculated by substituting the phase value _φ corresponding to the word reception time to the synchronization function F _Antisync (Φ) to the current phase Φ (step 511). Information on the reception time of the anti sync word is stored in the synchronization time information memory 1050.

As a result of this adjustment, the anti-sink word is not sent out periodically every period T, but is sent at a time point adjusted according to the time when the anti-sink word is received from the neighboring network terminal.

FIG. 11 is a diagram illustrating a PCO antiphase synchronization process when the network terminal 1000 includes two phase controllers to support PCO antiphase synchronization in order to increase accuracy. It is assumed that each of the phase controllers has a period T, and ΔΦ is set for the period T, so that Φ increases by ΔΦ per unit time.

Referring to FIG. 11, the first phase controller each increases the first phase Φ by ΔΦ per hour, and the second phase controller increases the second phase Φ ′ by ΔΦ per hour (step 601). If the phase Φ 'and the phase Φ have reached the threshold phase value for inducing the anti-sync word transmission (step 603), and if the threshold phase value has been reached, the synchronization signal transmitter 1025 is determined by determining the anti-sync word transmission time. In step 605, the anti-sync word is transmitted.

The phases Φ and phase Φ ', the variables A and B are reset (step 607), and the phases Φ and phase φ' are increased by ΔΦ per time (step 601).

If the current phase Φ and the phase Φ 'do not reach the threshold phase value, if the anti-sink word is received from the outside through the synchronization signal detector 1020 (step 609), the controller 1010 Corresponding to each phase controller 1030, the second phase value φ 'corresponding to the anti sync word reception time on the period T is added to the variable A (step 611), and the phase value 1-Φ remaining until the next anti sync word transmission. Is added to variable B, and the first phase Φ is adjusted by the sum of the value of ρ * (BA) obtained by multiplying the difference between variable B and variable A by the constant ρ and the second phase Φ '. (Step 611, step 613).

As described above, the network terminal 1000 having the phase controller 1030 supporting the PCO synchronization mechanism may perform synchronization in the physical layer, and the process of applying the CSMA-CA scheme using the same is as follows. .

An object of the present invention is to allow time intervals to be accessed by each network terminal to a minimum without overlapping with the coordinator. As described above, the PCO synchronization mechanism may be utilized for such an operation, and two embodiments may be configured in the present invention. The first embodiment uses only PCO antiphase synchronization, and the second embodiment uses both PCO antiphase synchronization and PCO phase synchronization.

The first embodiment applies a distributed unslotted CSMA-CA scheme for NBPAN. The WBAN is implemented by NBPAN, and each network terminal constituting the NBPAN includes one phase controller 1030. And it is assumed that phase controller 1030 responds to the anti sync word for PCO antiphase synchronization. For better understanding of the description, the assumption about the phase controller 1030 is assumed to be the same as in FIG. 10, and FIG. 12 is a diagram illustrating an example of application of a distributed non-slot CSMA-CA scheme for NBPAN in this case. That is, each network terminal 710, 720, 730, 740, 750 shown in FIG. 12 is configured similarly to the network terminal 1000, and the phase controller 1030 included in each network terminal 710, 720, 730, 740, 750 includes an oscillator having a period T, ΔΦ Is set according to the period T, so that the phase? Of the oscillator increases by?? Per unit time. In addition, the phase controller 1030 supports a synchronization function F _Antisync (Φ) for PCO antiphase synchronization which is phase adjusted in a negative direction when an anti sync word is received from another network terminal.

FIG. 12 illustrates a converged phase state using anti-sink words emitted by five network terminals 710, 720, 730, 740, and 750 from A to E. FIG. That is, the position of each of the network terminals 710, 720, 730, 740, 750 represents the phase at which each anti-sink word is transmitted in period T. Each network terminal 710, 720, 730, 740, 750 may set a resource access section (CAP) for each network terminal, that is, a data transmission section based on a point separated by a solid line, and operate according to a non-slot CSMA-CA scheme in the corresponding section. Done.

The resource access section for each network terminal 710, ₇₂₀ , 730, 740, 750 is designed so that the network terminals 710, 720, 730, 740, 750 can be varied in phase within the resource access section of each network terminal 710, 720, 730, 740, 750 in consideration of the phase change caused by F _Antisync (Φ). It is desirable to be.

Accordingly, since FIG. 12 _assumes that the F _Antisync (Φ) output value in anti-phase synchronization mainly acts as negative feedback (FIG. 10), it is possible to design a resource connection attempt after the anti-sync word launch time. have. For example, the network terminal A 710 sets a data transmission interval for attempting resource access in the interval between the network terminal E 750.

This operation allows devices to attempt to access resources at equally spaced intervals from each other, thereby significantly reducing the number of busy or collisioned channels. Therefore, nonslot CSMA-CA can be set more aggressively by increasing the size of packets sent at once or reducing the size of the backoff window to get more throughput.

Referring to Figure 15, the network terminal A (710) describes the process of applying a distributed unslotted (unslotted) CSMA-CA scheme for NBPAN as follows.

The CSMA-CA operation interval calculator 1040 in the network terminal A 710 requests the synchronization time information in step 801 under the control of the controller 1010, and the synchronization time information from the synchronization time information memory 1050 in step 803. Acquire it.

Synchronization time information is the most recent anti-sink word origination time of the network terminal A (710) and the most recent other network terminal, for example, network terminal B 720, network terminal C (730), network terminal D ( 740, the reception time point of the anti-sink word most recently received from any one of the network terminals E 750. The transmission time and the reception time of the anti-sync word are updated in real time in the PCO synchronization process (steps 803a and 803b). The update of the information about the transmission time and the reception time for the anti-sync word may be performed by the process of FIG. 10.

In operation 805, the CSMA-CA operation interval calculator 1040 calculates the size of the available resource access interval, for example, the length of the unslotted CSMA-CA operation interval. In other words, the most recently received anti-sync word reception time is compared with the most recent anti-sync word transmission time point, and the interval therebetween is calculated as the length of the available non-slot CSMA-CA operation period.

The controller 1010 checks whether the calculated non-slot CSMA-CA operation interval is greater than the effective transmission interval in step 807. If the calculated length of the non-slot CSMA-CA operation interval is less than the effective transmission interval, the process proceeds to step 801 and repeats the above process. This is because, if the calculated non-slot CSMA-CA operation interval is too short, it is practically unable to transmit data by attempting a resource connection.

If the length of the calculated non-slot CSMA-CA operation interval is greater than or equal to the effective transmission interval, the length of the final non-slot CSMA-CA operation interval is determined within the calculated non-slot CSMA-CA operation interval length. That is, the final resource access interval is determined. In this case, the length of the last non-slot CSMA-CA operation interval may be determined by the amount of data to be transmitted.

The start time of the final non-slot CSMA-CA operation section is selected in consideration of the period T of the oscillator and the transmission time of the synchronization signal so that the phase variation of the phase controller 1030 can be made in the final non-slot CSMA-CA operation section. It is desirable to be.

When the controller 1010 reaches the start of transmission of the determined final non-slot CSMA-CA operation interval in step 809, the controller 1010 starts the non-slot CSMA-CA operation in step 811. For example, steps 131 to 141 of FIG. 5B are performed. That is, when the non-slot CSMA-CA operation period starts, after the back off time, the CCA mode is performed to check whether the resource is used, and if the resource is not used, data is transmitted. In this case, a function for detecting the anti sync word in the CCA mode may be added in the physical layer. In this case, when the network terminal A 710 uses the CSMA-CA scheme to transmit packet data, if an anti-sink word is being transmitted from another network terminal, it will be detected in the CCA mode, and resource access again after backoff. Will try.

Thereafter, in step 813, the controller 1010 proceeds to step 815 when the transmission completion time according to the final non-slot CSMA-CA operation interval is reached, and stops the final non-slot CSMA-CA operation.

On the other hand, Figure 13 shows the F _Antisync (Φ) output value in the PCO anti-phase synchronization mainly acts as a positive and negative feedback, for example, in consideration of the embodiment of FIG. Another example of setting a resource access interval (CAP) in consideration of this. The resource access section corresponds to the non-slot CSMA-CA operation section. In the assumption of FIG. 11, since the phase of the phase controller may be adjusted in a positive direction or a negative direction after receiving an anti-sink word from the outside, the non-slot CSMA-CA operation period is the anti-sink word transmission time point. It is preferred to be designed to be determined back and forth.

Even if the time for starting the non-slot CSMA-CA is distributed by the above operation, the anti-sink word with neighboring devices may be affected if the amount of data to be sent by the device may affect the anti-sink word to be fired subsequently. Considering the phase difference, it is appropriate to control to stop the transmission in this period T appropriately. However, because each device is self-assessing, errors may occur, so it is necessary to make a safety device. Clear Channel Assessment (CCA), as defined by 802.15.4 or 802.11, is designed to detect sequences defined in the specification (eg sync symbols). If the ability to detect anti-sink words in CCA mode is added at the physical layer, when the device uses CSMA-CA to transmit packets, if anti-sink words are being sent from the device, they will be detected in the CCA phase. If there is more to send in this period T, it will try again after backoff. If there is nothing to send, this period T stops further transmission attempts.

The following is a distributed slotted CSMA-CA scheme for NBPAN as a second embodiment. In this case, each network terminal is equipped with two phase controllers 1030, one to respond to the sync word for PCO phase synchronization, and the other to respond to the anti sync word for PCO antiphase synchronization. It is supposed to. This embodiment is shown in FIG. 14. Each network terminal 760, 770, 780, 790, 800 shown in FIG. 14 is configured similarly to the network terminal 1000, and only supports PCO phase synchronization, and supports a phase controller that responds to a sync word, and supports PCO antiphase synchronization. Suppose you have a phase controller that responds to anti-sink words.

Accordingly, the configuration of the network terminal F 760 is shown in FIG. 18 is a diagram showing the configuration of a network terminal F 760 according to another embodiment of the present invention. Referring to FIG. 18, the network terminal F 760 is configured similarly to the network terminal 1000 and is different in that it includes a first phase controller 1033 and a second phase controller 1035. The first phase controller 1033 is a phase controller that supports PCO antiphase synchronization, and the first phase second controller 1035 is a phase controller that supports PCO phase synchronization. The configuration of four network terminals 770, 780, 790, and 800 from G to K is similar.

In addition, the first phase controller 1033 supports a synchronization function F _Antisync (Φ) for PCO antiphase synchronization which is phase adjusted in a negative direction when an anti sync word is received from another network terminal, and the second phase controller 1035. ) Is the synchronization function F _sync for PCO phase synchronization with phase adjustment in the positive direction Assume that '(Φ) is supported.

In FIG. 14, the anti-sink words emitted from five network terminals 760, 770, 780, 790, and 800 from F to J show converged phase states. In addition, at the same time, it shows a phase state in which sync words emitted from five network terminals 760, 770, 780, 790, and 800 from F to J are converged at a point indicated by R. Each network terminal 760, 770, 780, 790, 800 operates as a slot CSMA-CA in a device-specific resource access section (CAP) separated by a solid line. In order to operate with the slot CSMA-CA, the backoff slot boundary must be known. In the BPAN, the superframe information can be determined by receiving the beacon. However, the present invention assumes NBPAN. Can't. Instead, it calculates backoff slot boundaries based on itself on the sync word that each device fires. PCO phase synchronization between sync words converges to the same phase after a period of time, so all devices have the same time reference. Other operations are similar to distributed nonslot CSMA-CA.

Referring to FIG. 16, a process of applying a distributed slotted CSMA-CA scheme for NBPAN by the network terminal F 760 is as follows.

The CSMA-CA operation interval calculator 1040 at the network terminal F 760 requests synchronization time information in step 901 according to the control of the controller 1010, and synchronizes time information from the synchronization time information memory 1050 in step 903. Acquire it.

The synchronization time information is the most recent anti-sync word origination time of the network terminal F 760, and the network terminal G 770, the network terminal H 780, the network terminal I ( 790, a reception time point of an anti-sink word most recently received from any one of the network terminals J 800. The transmission time and reception time of the anti-sync word are updated in real time in the PCO synchronization process (steps 903a and 903b).

In step 905, the backoff slot boundary is set based on the origination time of the sync word transmitted by the second phase controller 1035. As shown in Fig. 14, when the PCO phase synchronization mechanism is used, the sync words emitted from five network terminals 760, 770, 780, 790, and 800 from F to J can converge at the point indicated by R (step 905a). The backoff slot boundary may be calculated based on the origination time of the sync word by the two-phase controller 1035.

In operation 906, the CSMA-CA operation section calculator 1040 calculates the size of the resource access section, for example, the length of the slotted CSMA-CA operation section. In other words, the most recently received anti-sync word reception time is compared based on its latest anti-sync word transmission time point, and the interval therebetween is calculated as the available slot CSMA-CA operation interval length.

The controller 1010 checks whether the calculated slot CSMA-CA operation duration is greater than or equal to the effective transmission duration in step 907. If the calculated length of the slot CSMA-CA operation interval is less than the effective transmission interval, the process proceeds to step 901 and repeats the above process. This is because, if the calculated slot CSMA-CA operation interval is too short, it is practically unable to transmit data by attempting a resource connection.

If the calculated length of the slot CSMA-CA operation interval is greater than or equal to the effective transmission interval, the length of the last slot CSMA-CA operation interval is determined within the calculated slot CSMA-CA operation interval length. In this case, the length of the last slot CSMA-CA operation interval may be determined by the amount of data to be transmitted.

The start time of the last slot CSMA-CA operation section is selected in consideration of the period T of the oscillator and the transmission time of the synchronization signal so that the phase shift of the first phase controller 1033 can be made in the last slot CSMA-CA operation period. It is desirable to be.

In step 909, the controller 1010 starts slot CSMA-CA operation in step 911 when it is time to start transmission of the determined final slot CSMA-CA operation period. That is, when the slot CSMA-CA operation period starts, after the backoff time, the backoff slot boundary is calculated based on the sync word itself. After performing the random backoff operation according to the backoff slot boundary, a CCA mode is performed to check whether the resource is used, and if the resource is not used, data is transmitted. In this case, a function for detecting the anti sync word in the CCA mode may be added in the physical layer. In this case, when the network terminal A 710 uses the CSMA-CA to transmit packet data, if an anti-sink word is being transmitted from another network terminal, it will be detected in the CCA mode, and the resource connection again after the backoff. Will try.

Thereafter, in step 913, when the transmission completion time according to the last slot CSMA-CA operation period arrives, the controller 1010 proceeds to step 915 to stop the last slot CSMA-CA operation.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. Therefore, the scope of the present invention should not be limited by the described embodiments but should be determined by the equivalents of the claims and the claims.

Claims (16)

In at least one network terminal device included in a wireless body area network (WBAN),
A first oscillator operating at a period T, the phase increasing in proportion to time, causing the first synchronization signal to be sent when the phase reaches a threshold phase value, and receiving the first synchronization signal from the outside, A first phase controller for performing PCO antiphase synchronization with the oscillator by performing phase adjustment of the oscillator according to a reception timing of the received first synchronization signal;
At least a part of the resource access section calculated using the originating time of the transmitted first synchronization signal and the reception time is determined as the last resource access section, and the phase adjustment of the oscillator is within the last resource access section. And a controller for determining a start time of the last resource access section and attempting to access a resource during the last resource access section to transmit data. The apparatus of claim 1, wherein the first phase controller adjusts the phase adjustment of the oscillator by adding a phase change amount calculated by inputting a current phase value of the oscillator corresponding to the reception time point to a synchronization function, to the current phase value. Network terminal device, characterized in that performed. The network terminal apparatus of claim 1, wherein the controller transmits data according to a CSMA-CA scheme during the last resource access interval. The network terminal apparatus of claim 1, wherein the controller determines the final resource access section when the calculated resource access section is equal to or greater than the effective transmission section. 4. The apparatus of claim 3, further comprising a second oscillator operating at a period T, wherein the phase increases in proportion to time, causing the second synchronization signal to be sent when the phase reaches a threshold phase value, and a second synchronization from outside. Receiving a signal, the second phase controller further performing a PCO phase synchronization with respect to the oscillator by performing phase adjustment of the second oscillator according to a reception timing of the received second synchronization signal,
And the controller sets a backoff slot boundary based on the second synchronization signal transmission time point in order to transmit data according to a slot CSMA-CA scheme. The network terminal device according to claim 1, further comprising a synchronization signal transmitter for transmitting the first synchronization signal under the control of the phase controller. The network terminal device according to claim 1, further comprising a synchronization signal detector for detecting the reception of the received first synchronization signal. The network terminal device according to claim 1, further comprising a synchronization time information memory for updating and storing information on the transmission time and the reception time. In the resource connection method of at least one network terminal device included in a wireless body area network (WBAN),
A phase controller including a first oscillator operating at a period T and whose phase increases in proportion to time causes the first synchronization signal to be sent when the phase reaches a threshold phase value and receives the first synchronization signal from the outside. Performing phase adjustment of the oscillator according to a reception time of the received first synchronization signal to perform PCO antiphase synchronization with respect to the oscillator;
Determining at least a part of a resource access section of the resource access section calculated using the originating time of the first synchronization signal and the reception time point as a final resource access section;
Determining a start time of the last resource access section so that the phase adjustment of the oscillator is within the last resource access section;
And attempting to access a resource during the last resource access period and transmitting data. 10. The apparatus of claim 9, wherein the first phase controller adjusts the phase adjustment of the oscillator by adding a phase change amount calculated by inputting a current phase value of the oscillator corresponding to the reception time point to a synchronization function, to the current phase value. Resource access method, characterized in that for performing. 10. The method of claim 9, wherein data is transmitted according to a CSMA-CA scheme during the last resource access interval. 10. The method of claim 9, wherein the last resource access interval is determined when the calculated resource access interval is greater than or equal to the effective transmission interval. 10. The method of claim 9, wherein the first phase controller, comprising a second oscillator operating at a period T and whose phase increases in proportion to time, causes a second synchronization signal to be sent when the phase reaches a threshold phase value, Receiving a second synchronization signal from an external source, performing phase adjustment of the second oscillator according to a reception time of the received second synchronization signal, and performing PCO phase synchronization with respect to the oscillator;
And setting a backoff slot boundary based on the second synchronization signal transmission time point to transmit data according to a slot CSMA-CA scheme. 10. The method of claim 9, wherein the first synchronization signal is transmitted through a synchronization signal transmitter. 10. The method of claim 9, wherein the reception of the received first synchronization signal is detected through a synchronization signal detector. 10. The method of claim 9, wherein the information on the transmission time and the reception time is updated and stored in the synchronization time information memory.

Images