CN101277271A - Power Controllable Distributed CDMA Network Media Access Control Method - Google Patents

Abstract

A power controllable distributed CDMA network media access control method. With the present invention, when the node has data to send, the common code is used to send the RTS packet, the receiving node uses the common code to receive the RTS packet sent by the sending node, and the SNR of the packet is counted, if the SNR is greater than or equal to the threshold SNR , the receiving node feeds back power control information to the sending node through the CTS packet; otherwise, the receiving node does not send back the CTS packet, and the sending node increases the transmission power to resend the RTS packet. After receiving the CTS packet, the sending node adjusts the transmit power to send the data packet to the receiving node. After the receiving node receives the data packet, it replies with an ACK packet. When the network node has no data to send, the common code is used to receive the control packet, and corresponding processing is performed according to the type of the received control packet. The invention can effectively reduce the average transmission power of the network nodes, improve the spatial multiplexing degree of the network, and further increase the network throughput without increasing the node hardware cost.

Description

Power Controllable Distributed CDMA Network Media Access Control Method

technical field

The present invention relates to a distributed CDMA network medium access control method with controllable power, in particular to a distributed CDMA network medium access control method with controllable power by using common spreading codes to interactively control groups. The invention belongs to the technical field of distributed network media access control.

Background technique

In distributed wireless communication networks such as self-organizing networks (Ad Hoc), wireless sensor networks, grid networks (mesh networks), and multi-hop cellular networks, there is generally no central control station, so the use of wireless resources cannot be centralized. For unified scheduling and allocation, each network node can only decide whether and how to use wireless communication resources. The rules and basis for network nodes to use wireless communication resources have an important impact on network throughput and resource utilization efficiency. Especially in a multi-hop distributed wireless network, the data packet sent by the source node may need to be forwarded by the intermediate node to reach the target node. In this way, not only the source node needs to adopt certain rules to compete with adjacent nodes for using wireless resources, but also the intermediate nodes also need to compete for using wireless resources in order to complete the forwarding task. Any conflict that occurs when using wireless resources will cause data packets to be incorrect. Or transmit in time. The competitive use rules of wireless resources are usually determined by the media access control method adopted by network nodes, so designing a reasonable media access control method is of great significance for improving the resource utilization efficiency of distributed wireless networks, and then improving the throughput performance of the network .

In order to improve the utilization efficiency of wireless resources in a distributed network, it is generally necessary to implement spatial multiplexing of wireless resources. The degree of spatial multiplexing of wireless resources has an important relationship with the transmit power of network nodes. By limiting the transmit power of network nodes, the transmission radius (also called one-hop coverage) of the transmitted signal of the node can be roughly estimated. Those network nodes outside the radius can adopt the same wireless resource usage rules as the source node without being affected by the signal transmitted by the source node, which forms the spatial multiplexing of wireless resources. For a certain wireless resource bandwidth and a given entire network coverage, if the transmission power of the network node is large, the number of spatial multiplexing is small, and the data packet can reach the target node only after a small number of forwarding times. In this sense, the data packet transmission efficiency is higher, and it is possible to achieve higher network throughput. But on the other hand, the reduction in the number of spatial multiplexing means that each time when competing for wireless resources, there are more competitors, and the possibility of failure in the competition is greater, so the network throughput tends to decrease. These interactions and mutual influence relationships show that: the transmit power of network nodes will affect the degree of spatial multiplexing of wireless resources, and then affect the throughput of the network.

For a multi-hop distributed wireless communication network that uses Code Division Multiple Access (CDMA: Code Division Multiple Access) technology for signal transmission and reception, on the one hand, a network node can share wireless resources with its adjacent network nodes at the same time, thus simplifying On the other hand, the greater the number of network nodes sharing wireless resources at the same time, the greater the mutual interference, and the greater the difficulty for the receiver of the target node or forwarding node to recover the signal. Therefore, it is still necessary to reduce the number of nodes that may use wireless resources at the same time by means of spatial multiplexing. However, at this time, the transmit power of network nodes not only determines the degree of spatial multiplexing of the network, but also affects the interference power of other nodes within the coverage of one hop, thus significantly affecting the successful transmission of data packets of other nodes. The specific performance is: if the transmission power of each network node is specified to be the same, then a larger transmission power is beneficial to the data reception of a specific target node (including the forwarding node), but at this time the transmission power of the neighboring nodes sharing wireless resources is also Larger, the transmission power of multiple sharing nodes will generate greater interference, which in turn is unfavorable to the data packet reception of the target node. The self-interference problem of CDMA system is solved by open-loop power control and closed-loop power control in mobile communication systems. These power control methods are usually scheduled and implemented by the centralized controller in the network—the base station. However, in a distributed wireless communication network, since there is no dedicated centralized controller to complete the functions of the base station, the centralized power control method is not applicable, and only a node power scheduling method suitable for a distributed CDMA network can be designed.

Through literature retrieval to the prior art, it is found that "Power controlled dual channel (PCDC) medium access protocol for wireless Ad Hoc networks," published by A.Muqattash et al. in "IEEE INFOCOM'2003" pp.470-480, 2003, ( IEEE 2003 International Conference on Information and Communication, March 2003, pages 470 to 480, a power-controlled dual-channel media access control protocol for Ad Hoc networks), proposed a dual-channel-based power regulation In this method, each node uses two different frequency channels to send control packets and data packets, which requires each node to be able to listen to data on one channel and send data on another channel at the same time, to achieve this This function needs to equip each node with two transceiver modules, which is difficult to realize. "Jointopportunistic power scheduling and end-to-end rate control for wireless Ad Hocnetworks" ( IEEE Transactions on Automotive Electronics, March 2007, Volume 56, pages 801 to 809, joint opportunistic power scheduling and end-to-end rate control in wireless Ad Hoc networks) proposed joint power scheduling and end-to-end rate control node power scheduling algorithm, this method solves the power scheduling problem of the Ad Hoc network to a certain extent, but this method requires a central controller in the network to implement the power and rate scheduling algorithm, because the nodes in the Ad Hoc network It is a peer-to-peer node, and there is no central node that performs scheduling functions, so the method proposed in this paper is difficult to implement in the actual design of Ad Hoc networks.

Contents of the invention

The purpose of the present invention is to propose a power-controllable distributed CDMA network media access control method, which is used to realize distributed scheduling of network node transmission power without increasing the hardware cost of network nodes, and then improve distributed CDMA. The throughput performance of the network. The present invention defines some rules that network nodes should follow when sharing wireless resources for information interaction. By executing these rules, each network node can self-configure the required sending and receiving spreading codes, and at the same time determine and adjust their own signal transmission power. Furthermore, the energy consumption of network nodes is reduced, the spatial multiplexing degree of the distributed CDMA network is improved, and the throughput of the network is increased.

The invention is applicable to self-organizing network, grid network (mesh network), multi-hop cellular network and wireless sensor network adopting self-organizing way of networking. In the present invention, the following points need to be emphasized: First, in the present invention, the network node only needs to have one sender and one receiver, and the sender and receiver work in the same half-duplex mode. Frequency band; Second, in the present invention, so-called sending node is the node that points to receiving node to send data grouping, and so-called data grouping includes the data grouping that this sending node self produces and the data grouping that forwards for other nodes, and so-called receiving node refers to data grouping. Packet forwards the desired destination node through each hop; the 3rd, in the present invention, requires each node to be equipped with a spread spectrum transceiver, and this transceiver can update the spread spectrum code as required; the 3rd, in In the present invention, each node is required to have the ability to count the signal-to-noise ratio of the received control packet; the 4th, in the present invention, the network node is required to have a power adjustment function, and the transmission power can be adjusted as required; the 5th, this method is applicable to Slow fading channel, that is, the channel gain remains unchanged within a transmission period of a control packet and a data packet; sixth, the link between the sending node and the destination node has bidirectional characteristics, that is, the link between the sending node and the destination node And the link between the destination node and the sending node has the same channel gain.

The present invention is achieved through the following technical solutions:

A power-controllable distributed CDMA network media access control method, comprising two parts: an access method when a network node has data packets to send and an access method when the network node has no data packets to send, when the network node When there are data packets to be sent, the access method is:

a.1 The sending node A takes out the data packet from the waiting packet queue of the node, and determines that the receiving node is the node B pointed to by the target address in the data packet according to the target address in the data packet;

a.2 The sending node A sends a request to the receiving node B to send an RTS packet using the common code. The RTS packet includes a type field, a source address field, a source node user code field, a target address field, and a transmission power field, where the type field is filled in The identification code indicating that the packet is an RTS packet, the source address field is filled with the address of sending node A, the source node user code field is filled with the user code of sending node A, the target address field is filled with the address of receiving node B, and the transmit power field is filled with The transmission power PT used by the sending node A to send the RTS packet, PT=Pp, Pp is the initial transmission power of the network node, and the functional relationship Pp=f(SIRp ), f(x) represents the function mapping relationship, the mapping relationship between the value of f(x) and x is determined by the noise power in the network and the radius of the average one-hop coverage of the network node; SIRp is determined by the network node Determine the channel codec scheme, modulation and demodulation scheme, and the data bit transmission error probability that the receiver can allow; sending node A starts timing and enters step a.6;

a.3 The receiving node B uses the common code to receive and despread the RTS packet sent by the sending node A, and obtains the signal-to-noise ratio (SIRs) of the RTS packet through statistics, and takes out the user code of the source node in the RTS packet to update the user code selected by the receiving node B. user code;

a.4 Compare the RTS packet signal-to-noise ratio SIRs obtained in step a.3 with the threshold signal-to-noise ratio SIRp predetermined by the network. If SIRs<SIRp, the receiving node B does not send a clear-to-send CTS packet to the sending node A, and enters the step a.3; otherwise, the receiving node B calculates the redundant signal-to-noise ratio SIRa, SIRa=SIRs-SIRp, and according to the value PT of the transmitting power field in the RTS packet described in step a.2, determines that the transmitting power of the receiving node B is PT-f(SIRa);

a.5 The receiving node B sends a CTS packet to the sending node A with the transmit power PT-f(SIRa) determined in step a.4; the CTS packet includes a type field, a source address field, a target address field, and a transmit power field, wherein Fill in the identification code indicating that the packet is a CTS packet in the type field, fill in the address of receiving node B in the source address field, fill in the address of sending node A in the target address field, fill in the receiving node B determined in step a.5 in the transmit power field The transmit power value PT-f(SIRa);

a.6 If sending node A receives the CTS packet sent by receiving node B within Tt time, then enter step a.7, otherwise, sending node A enters step a.9;

a.7 Sending node A determines the transmit power used by sending node A when sending data packets to receiving node B subsequently according to the value of the transmit power field in the CTS packet received in step a.6, the value of the transmit power Get the value of the transmit power field in the CTS packet;

a.8 The sending node A uses the user code of the node A and the transmission power determined in step a.7 to send the data packet to the receiving node B, and the receiving node B uses the user code determined in step a.3 to receive and despread the data packet, Then send an acknowledgment ACK packet to the sending node A;

a.9 Sending node A increases the transmission power by dt, and increases the value of the transmission power field in the RTS packet by dt. When the cumulative number of repeated transmissions is less than the maximum allowable number of repeated transmissions Rm, and the transmission power is less than or equal to the maximum allowable transmission power, send Node A resends an RTS packet to receiving node B with the transmission power after dt is increased, and returns to step a.6, otherwise, treat receiving node B as unreachable;

a.10 The receiving node B is unreachable, the sending node A adds the data packet to the queue of the node waiting to send the packet, and re-enters step a.1;

When the network node has no data packets to send, the access method is:

b.1 Network node A uses the common code to receive and despread the control packet, and obtains the signal-to-noise ratio of the received control packet as SIRs through statistics; judges whether the received control packet is an RTS packet according to the value of the type field in the received control packet, if If the received control packet is an RTS packet, proceed to step b.2, otherwise, network node A re-executes step b.1;

b.2 Determine whether the address of the network node A is the same as the target address in the RTS packet. If not, the network node A determines that the channel is busy, and after a delay of Δt, re-execute step b.1; otherwise, take out the RTS packet The user code of the source node updates the user code of node A in this network;

b.3 Compare the receiving control packet signal-to-noise ratio SIRs obtained in step b.1 with the threshold signal-to-noise ratio SIRp predetermined by the network. The allowable data bit transmission error probability is determined; if SIRs<SIRp, then network node A enters step b.1; otherwise, network node A calculates the redundant signal-to-noise ratio SIRa, SIRa=SIRs-SIRp, and receives according to step b.1 The value PT of the transmission power field in the control packet determines that the transmission power of the network node A is PT-f(SIRa), f(x) represents the function mapping relationship, and the mapping relationship between the value of f(x) and x is given by The noise power in the network and the radius of the average one-hop coverage of network nodes are determined;

b.4 Send CTS packet to the node sending RTS packet in step b.1 with the node transmission power PT-f(SIRa) determined in step b.3; the source address field of CTS packet is filled with the address of network node A, and the destination address Field fills in the address of the node that sends RTS packet in step b.1, transmits the power field and fills in the node transmission power value PT-f (SIRa) that step b.3 determines;

b.5 After the node sending the RTS packet in step b.1 receives the CTS packet, it uses the user code of the node and the transmit power determined by the transmit power field in the CTS packet to send a data packet to the network node A, and the network node A receives After the data packet, send an ACK packet to the node that sent the RTS packet in step b.1.

In the power-controllable distributed CDMA network media access control method, the spreading code configuration method adopted is as follows: the network configures Ns spreading codes in total, and one of the spreading codes is used as a common spreading code, referred to as the common code , the spreading code is used to send control packets and is known to each network node; the remaining Ns-1 spreading codes are used as user spreading codes, referred to as user codes, for sending data packets; when the network node initializes Configure the spreading code as a common code, and at the same time randomly select and set a user code as the initial user code of the node, and the network node can update the user code of the node as needed; the rule for the network node to update the user code of the node is: if received If the control group is an RTS group, and the address of the node is the same as the address of the target node in the RTS group, the user code of the node is updated to the user code of the source node in the RTS group; otherwise, the user code of the node remains the initial user of the node code.

Compared with prior art, the present invention has following advantage:

The invention provides a power controllable distributed CDMA network medium access control method. When network nodes are exchanging information, by using this access control method, each network node can self-configure the required sending and receiving spreading codes, and at the same time determine and adjust the transmission power used when sending packets. In the present invention, each network node only needs one transmitter and one receiver, the hardware cost of the network node does not increase, and the present invention does not require the network to have a centralized control node that executes the power scheduling algorithm, and realizes the transmission of network nodes Distributed scheduling of power. Compared with other media access control methods used in distributed CDMA networks, the present invention can not only ensure the normal operation of distributed CDMA networks, but also has the function of controlling the transmission power of network nodes, which can effectively reduce the average transmission power of network nodes and reduce The energy consumption of the network nodes improves the spatial multiplexing degree of the distributed network, thereby increasing the network throughput, and the invention has a simple principle and is easy to be used in distributed CDMA network communication terminals.

Description of drawings

Fig. 1 shows a specific embodiment of the application of the present invention. There are four network nodes A, B, C, and D in the figure. Node A will transmit information with node B, A is the sending node, and B is the receiving node. R is the radius of the average one-hop coverage of network nodes.

Fig. 2 shows the control packet frame structure adopted by the present invention. The control packets used in the present invention include request to send RTS packets, clear to send CTS packets, and confirm ACK packets.

Fig. 3 shows an access flow chart executed when a network node has a data packet to be sent.

Figure 4 shows an access flow diagram performed when the network node has no data to send.

Detailed ways:

The working principle of the present invention will be described in detail below in conjunction with the accompanying drawings.

In order to realize the power control of distributed CDMA network nodes so as to facilitate more effective information exchange between network nodes, the packets transmitted on the channel are divided into two types: control packets and data packets. The control packet completes the control signaling transmission, supports the spread spectrum code configuration function of the network node, and the node transmit power determination and adjustment function; the data packet is used to transmit business data, and the required spread spectrum code and transmit power are transmitted by the control packet The message decides.

There are three types of control packets on the channel, which are request to send RTS packet, clear to send CTS packet and confirmation ACK packet. The format of various control groups is shown in Figure 2, and the meanings of each part are as follows:

Type: It is used to identify the type of control packet. Different identification codes can be set to indicate RTS packet, CTS packet, and ACK packet respectively; Packet length: Used to describe the number of bits contained in the control packet; Source address: Indicates that the control packet is sent The node address of the packet; the user code of the source node: indicates the user code used by the node sending the control packet; the target address: indicates the address of the node to which the control packet will be sent; transmit power: used to indicate when the node transmits the control packet Transmit power used; CRC: redundancy check.

The medium access control method with power control function in the distributed CDMA network that the present invention proposes, its specific implementation mode is as follows:

1. Configure initialization parameters for network nodes. Before the network node accesses the channel to initiate information transmission, it is necessary to initialize the network node, assign a node address for each node in the network, set the initial transmission power, and configure the initial spreading code, mainly including the following:

a. Assign each node in the network a unique physical address or ID identification different from other nodes, called node address.

b. Set an initial transmit power Pp for each node in the network. The functional relationship Pp=f(SIRp) is satisfied between the node’s initial transmit power Pp and the predetermined threshold signal-to-noise ratio SIRp of the network, f(x) represents the functional mapping relationship, and the mapping relationship between the value of f(x) and x is given by The noise power in the network and the radius of the average one-hop coverage of network nodes are determined. If K represents the antenna gain between transceivers, R represents the radius of the average one-hop coverage of network nodes, and W represents the noise power in the network, then f(x)=WR ^η /K x, where η is the path Attenuation index, so the initial transmit power of the node is Pp=f(SIRp)=WR ^η /K·SIRp. SIRp is determined by the channel codec scheme, modulation and demodulation scheme adopted by the network node, and the data bit transmission error probability that the receiver can allow. For example, if the network node uses BPSK modulation, the data bit transmission error probability that the receiver can allow is p _b =10 ^-5 , in the case of not using channel coding, the predetermined threshold signal-to-noise ratio of the network should take SIRp=9.6dB.

c. Configure an initial spreading code for each node in the network. The distributed CDMA network of the present invention is configured with Ns spreading codes l ₁ , l ₂ , ..., l _Ns , Ns is a positive integer, and one of the spreading codes is used as a common spreading code, referred to as a common code, for each Known by network nodes, they are used for sending or receiving control packets by network nodes; the remaining Ns-1 spreading codes are used as user spreading codes, referred to as user codes, and are used for sending or receiving data packets by network nodes. When the network node is initialized, the spreading code is configured as a common code, and at the same time, a user code is randomly selected and set as the initial user code of the node. When sending or receiving data packets subsequently, the network node can update the user code of the node as required. The network node first uses the common code to send and receive the control packet, and negotiates to determine the user code used when sending or receiving the data packet through the information carried in the control packet. The rule for the network node to update the user code of this node is: if the received control packet is an RTS packet, and the address of this node is the same as the address of the target node in the RTS packet, then update the user code of this node to the user of the source node in the RTS packet code; otherwise, the user code of this node remains as the initial user code of this node.

2. The overall process of information transmission between network nodes is as follows: After the network node completes the initialization, it enters the formal communication stage. When the node has data to send, it uses the public code to send a request to send an RTS packet, and the receiving node uses the public code to receive and despread For the RTS packet sent by the sending node, the SNR of the packet is counted. If the SNR is greater than or equal to the threshold SNR, the receiving node feeds back the power control information to the sending node by clearing the sent CTS packet; otherwise, the receiving node does not send back the CTS packet. The sending node increases the transmission power and resends the RTS packet. After receiving the CTS packet, the sending node readjusts the transmit power according to the value of the transmit power field in the CTS packet, and sends the data packet to the receiving node. After the receiving node receives the data packet, it replies to confirm the ACK packet, so far the information transmission process is completed. When the network node has no data to send, use the common code to receive and despread the control packet, and make corresponding processing according to the type of the control packet and the information contained therein.

3. A power-controllable distributed CDMA network media access control method, comprising two parts: an access method when a network node has a data packet to send and an access method when a network node does not have a data packet to send, as shown in FIG. As shown in 3, when the network node has a data packet to send, the access method is:

a.1 The sending node A takes out the data packet from the waiting packet queue of the node, and determines that the receiving node is the node B pointed to by the target address in the data packet according to the target address in the data packet;

a.2 The sending node A sends a request to the receiving node B to send an RTS packet using the common code. The RTS packet includes a type field, a source address field, a source node user code field, a target address field, and a transmission power field, where the type field is filled in The identification code indicating that the packet is an RTS packet, the source address field is filled with the address of sending node A, the source node user code field is filled with the user code of sending node A, the target address field is filled with the address of receiving node B, and the transmit power field is filled with The transmission power PT used by the sending node A to send the RTS packet, PT=Pp, Pp=WR ^η /K SIRp is the initial transmission power of the network node, SIRp is the threshold signal-to-noise ratio predetermined by the network, and SIRp is the channel used by the network node Determine the codec scheme, modulation and demodulation scheme, and data bit transmission error probability that the receiver can allow; sending node A starts timing and enters step a.6;

a.3 The receiving node B uses the common code to receive and despread the RTS packet sent by the sending node A, and obtains the signal-to-noise ratio (SIRs) of the RTS packet through statistics, and takes out the user code of the source node in the RTS packet to update the user code selected by the receiving node B. user code;

a.4 Compare the RTS packet signal-to-noise ratio SIRs obtained in step a.3 with the threshold signal-to-noise ratio SIRp predetermined by the network. If SIRs<SIRp, the receiving node B does not send a clear-to-send CTS packet to the sending node A, and enters the step a.3; otherwise, the receiving node B calculates the redundant signal-to-noise ratio SIRa, SIRa=SIRs-SIRp, and according to the value PT of the transmitting power field in the RTS packet described in step a.2, determines that the transmitting power of the receiving node B is PT-f(SIRa)=PT-WR ^η /K·SIRa;

a.5 The receiving node B sends a CTS packet to the sending node A with the transmit power PT-f(SIRa) determined in step a.4; the CTS packet includes a type field, a source address field, a target address field, and a transmit power field, wherein Fill in the identification code indicating that the packet is a CTS packet in the type field, fill in the address of receiving node B in the source address field, fill in the address of sending node A in the target address field, fill in the receiving node B determined in step a.5 in the transmit power field The transmit power value PT-f(SIRa);

a.6 If the sending node A receives the CTS packet sent by the receiving node B within the time Tt, then go to step a.7, otherwise, the sending node A goes to step a.9. Take Tt=2ts+2tp here, ts is the sending time of CTS packet or RTS packet, tp is the propagation delay experienced by wireless signal transmission from sending node A to receiving node B, or from receiving node B to sending node A.

a.7 Sending node A determines the transmit power used by sending node A when sending data packets to receiving node B subsequently according to the value of the transmit power field in the CTS packet received in step a.6, the value of the transmit power Get the value of the transmit power field in the CTS packet;

a.8 The sending node A uses the user code of the node A and the transmission power determined in step a.7 to send the data packet to the receiving node B, and the receiving node B uses the user code determined in step a.3 to receive and despread the data packet, Then send an acknowledgment ACK packet to the sending node A;

a.9 Sending node A increases the transmission power by dt, and increases the value of the transmission power field in the RTS packet by dt. When the cumulative number of repeated transmissions is less than the maximum allowable number of repeated transmissions Rm, and the transmission power is less than or equal to the maximum allowable transmission power, send Node A resends an RTS packet to receiving node B with the transmission power increased by dt, and returns to step a.6, otherwise, treat receiving node B as unreachable. If Pm is used to represent the maximum allowable transmit power, then the maximum allowable number of repeated transmissions and the increase or decrease range of transmit power dt should satisfy the relationship: Rm×dt=Pm-Pp, Pp is the initial transmit power of the network node, and Rm is a positive integer.

a.10 The receiving node B is unreachable, the sending node adds the data packet to the queue of the node waiting to send the packet, and re-enters step a.1;

When the network node has no data packets to send, the access method is:

b.1 Network node A uses the common code to receive and despread the control packet, and obtains the signal-to-noise ratio of the received control packet as SIRs through statistics; judges whether the received control packet is an RTS packet according to the value of the type field in the received control packet, if If the received control packet is an RTS packet, proceed to step b.2, otherwise, network node A re-executes step b.1;

b.2 Determine whether the address of the network node A is the same as the target address in the RTS packet. If not, the network node A determines that the channel is busy, and after a delay of Δt, re-execute step b.1; otherwise, take out the RTS packet The user code of the source node updates the user code of node A on the local network. Here, Δt=2ts+2tp is taken, ts is the sending time of the CTS packet or RTS packet, tp is the wireless signal from the node sending the RTS packet, that is, the sending node, to the target node that the RTS packet needs to be delivered, that is, the receiving node, or from the receiving node The propagation delay experienced by a node to transmit to the sending node.

b.3 Compare the receiving control packet signal-to-noise ratio SIRs obtained in step b.1 with the threshold signal-to-noise ratio SIRp predetermined by the network. The allowable data bit transmission error probability is determined; if SIRs<SIRp, then network node A enters step b.1; otherwise, network node A calculates the redundant signal-to-noise ratio SIRa, SIRa=SIRs-SIRp, and receives according to step b.1 The value PT of the transmission power field in the control packet determines that the transmission power of the network node A is PT-f(SIRa), f(x) represents the function mapping relationship, and the mapping relationship between the value of f(x) and x is given by The noise power in the network and the radius of the average one-hop coverage of network nodes are determined. If K represents the antenna gain between transceivers, R represents the radius of the average one-hop coverage of network nodes, and W represents the noise power in the network, then f(x)=WR ^η /K x, η is the path loss Index, so f(SIRa)=WR ^η /K·SIRa;

b.4 Send CTS packet to the node sending RTS packet in step b.1 with the node transmission power PT-f(SIRa) determined in step b.3; the source address field of CTS packet is filled with the address of network node A, and the destination address Field fills in the address of the node that sends RTS packet in step b.1, transmits the power field and fills in the node transmission power value PT-f (SIRa) that step b.3 determines;

b.5 After the node sending the RTS packet in step b.1 receives the CTS packet, it uses the user code of the node and the transmit power determined by the transmit power field in the CTS packet to send a data packet to the network node A, and the network node A receives After the data packet, send an ACK packet to the node that sent the RTS packet in step b.1. In the power-controllable distributed CDMA network media access control method, the spreading code configuration method adopted is as follows: the network configures Ns spreading codes in total, and one of the spreading codes is used as a common spreading code, referred to as the public spreading code. code, which is used to send control packets and is known to each network node; the remaining Ns-1 spread codes are used as user spread codes, referred to as user codes, for sending data packets; network nodes are initialized When configuring the spread spectrum code as a common code, at the same time randomly select and set a user code as the initial user code of the node, the network node can update the user code of the node according to the needs; the rule for the network node to update the user code of the node is: if receiving If the received control packet is an RTS packet, and the address of this node is the same as the address of the target node in the RTS packet, the user code of this node is updated to the user code of the source node in the RTS packet; otherwise, the user code of this node remains the initial user code.

The working principle of the present invention will be further described in conjunction with a specific embodiment of the present invention shown in FIG. 1 . There are four network nodes A, B, C, and D in the figure. Node A will transmit information with node B, A is the sending node, and B is the receiving node. R is the radius of the average one-hop coverage of network nodes.

1. Configure initialization parameters for network nodes. Before the network node accesses the channel to initiate information transmission, the network node needs to be initialized, mainly including the following:

a. Assign a unique physical address or ID to the four network nodes A, B, C, and D respectively, which is called the node address, recorded as: A ₁ , B ₁ , C ₁ , D ₁ .

b. Set the initial transmit power Pp for the four network nodes A, B, C, and D. The functional relationship Pp=f(SIRp) is satisfied between the node’s initial transmit power Pp and the predetermined threshold signal-to-noise ratio SIRp of the network, f(x) represents the functional mapping relationship, and the mapping relationship between the value of f(x) and x is given by The noise power in the network and the radius of the average one-hop coverage of network nodes are determined. If K represents the antenna gain between transceivers, R represents the radius of the average one-hop coverage of network nodes, and W represents the noise power in the network, then f(x)=WR ^η /K x, where η is the path Attenuation index, so the initial transmit power of the node is Pp=f(SIRp)=WR ^η /K·SIRp. SIRp is determined by the channel codec scheme, modulation and demodulation scheme adopted by the network node, and the data bit transmission error probability that the receiver can allow.

c. Configure initial spreading codes for the four network nodes A, B, C, and D. Apply the distributed CDMA network of the present invention to configure Ns spread spectrum codes l ₁ , l ₂ ,..., l _Ns , Ns is a positive integer, select l _Ns as common spread spectrum codes, referred to as common codes, for each network Known by the nodes, they are used for sending or receiving control packets by network nodes; the remaining Ns-1 spreading codes are used as user spreading codes, referred to as user codes, and are used for sending or receiving data packets by network nodes. After initialization, the initial user codes configured by nodes A, B, C, and D are l ₁ , l ₂ , l ₃ , and l ₄ respectively.

d. Set various identification codes to represent various control packets, use 00 to represent RTS packets, 01 to represent CTS packets, and 10 to represent ACK packets.

2. Apply the power controllable distributed CDMA network media access control of the present invention, when network node A needs to send data packet to network node B, the access method of execution is divided into following several steps:

Step 1: The sending node A takes out the data packet from the waiting packet queue of the node, and determines the receiving node as the node B pointed to by the target address B ₁ in the data packet according to the target address B ₁ in the data packet.

Step 2: The sending node A uses the common code l _Ns to send a request to the receiving node B to send an RTS packet. The type field of the RTS packet is filled with 00, the source address field is filled with A ₁ , the source node user code field is filled with l ₁ , and the target Fill in B ₁ in the address field, fill in the transmit power PT used by sending node A to send the RTS packet in the transmit power field, PT=Pp, Pp=WR ^η /K·SIRp is the initial transmit power of the network node, and SIRp is the predetermined threshold of the network SNR. The sending node A starts timing, and enters the sixth step.

Step 3: The receiving node B uses the common code _lNs to receive and despread the control packet, and obtain the SIRs of the RTS packet through statistics; according to the value 00 of the type field in the received control packet, determine whether the received control packet is an RTS packet , and according to the value B ₁ of the target address field of the received control packet, it is determined that the address of the node B is the same as the target address, and the receiving node B takes out the user code l ₁ of the source node in the RTS packet to update the user code selected by the receiving node B. At the same time, the network node C receives and despreads the control packet using the common code l _Ns , and obtains the signal-to-noise ratio SIRs of the RTS packet through statistics; according to the value 00 of the type field in the received control packet, it is judged whether the received control packet is an RTS packet , and according to the value B ₁ of the target address field of the received control packet, it is judged that the address of the node B is different from the target address, and the node C judges that the channel is busy, and after a delay of Δt=2ts+2tp, the public code l _Ns is used again to receive and despread Grouping is controlled and processed accordingly. At this time, node D also uses the common code _lNs to receive and despread the control packet, but because node D is far away from node A and is outside the one-hop coverage of node A, it cannot receive the RTS packet sent by node A, so Node D does not do any processing, and continues to receive and despread control packets using the common code l _Ns .

Step 4: The receiving node B compares the RTS packet signal-to-noise ratio SIRs obtained in step 3 with the threshold signal-to-noise ratio SIRp predetermined by the network. If SIRs<SIRp, the receiving node B does not send a clear-to-send CTS packet to the sending node A, Enter step three; otherwise, the receiving node B calculates the redundant signal-to-noise ratio SIRa, SIRa=SIRs-SIRp, and according to the value PT of the transmitting power field in the RTS packet described in step two, determines that the transmitting power of the receiving node B is PT- f(SIRa) = PT-WR ^η /K·SIRa.

Step 5: The receiving node B sends a CTS packet to the sending node A with the transmit power PT-f(SIRa) determined in step 4; the type field of the CTS packet is filled with 01, the source address field is filled with B1, and the target address field is filled with A _1. The transmit power field is filled with the transmit power value PT-f(SIRa) of the receiving Node B determined in Step 5. At the same time, the network node D uses the common code l _Ns to receive and despread the control packet, and obtains the signal-to-noise ratio SIRs of the RTS packet through statistics; according to the value 01 of the type field in the received control packet, it is judged that the received control packet is a CTS packet , node D reuses the common code l _Ns to receive and despread the control packet.

Step 6: If the sending node A receives the CTS packet sent by the receiving node B within Tt=2ts+2tp, then go to step 7; otherwise, the sending node A goes to step 9.

Step 7: The transmitting node A determines the transmitting power used by the transmitting node A when sending the data packet to the receiving node B according to the value of the transmitting power field in the CTS packet received in step 6, and the value of the transmitting power is taken as The value of the transmit power field in the CTS packet.

Step 8: The sending node A uses the user code _l1 of the node A and the transmission power determined in step 7 to send the data packet to the receiving node B, and the receiving node B uses the user code _l11 to receive and despread the data packet, and then send the data packet to the sending node A sends an acknowledgment ACK packet.

Step 9: Sending node A increases the transmission power by dt, and increases the value of the transmission power field in the RTS packet by dt. When the accumulated number of repeated transmissions is less than the maximum allowable number of repeated transmissions Rm, and the transmission power is less than or equal to the maximum allowable transmission power, The sending node A re-sends an RTS packet to the receiving node B with the transmission power increased by dt, and returns to step six, otherwise, the receiving node B is treated as unreachable. If Pm is used to represent the maximum allowable transmit power, then the maximum allowable number of repeated transmissions and the increase or decrease range of transmit power dt should satisfy the relationship: Rm×dt=Pm-Pp, Pp is the initial transmit power of the network node, and Rm is a positive integer.

Step 10: The receiving node B is unreachable, the sending node A adds the data packet to the queue of the node waiting to send the packet, and re-enters step 1.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. It should be understood by those skilled in the art that various other changes and substitutions can be made without departing from the spirit and principles of the present invention. and add. Therefore, within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (2)

1. A power-controllable distributed CDMA network media access control method, comprising two parts: an access method when network nodes have data packets to send and network nodes when there are no data packets to send, wherein It is characterized in that when the network node has a data packet to send, the access method is: a.1 The sending node A takes out the data packet from the waiting packet queue of the node, and determines that the receiving node is the node B pointed to by the target address in the data packet according to the target address in the data packet; a.2 The sending node A sends a request to the receiving node B to send an RTS packet using the common code. The RTS packet includes a type field, a source address field, a source node user code field, a target address field, and a transmission power field, where the type field is filled in The identification code indicating that the packet is an RTS packet, the source address field is filled with the address of sending node A, the source node user code field is filled with the user code of sending node A, the target address field is filled with the address of receiving node B, and the transmit power field is filled with The transmission power PT used by the sending node A to send the RTS packet, PT=Pp, Pp is the initial transmission power of the network node, and the functional relationship Pp=f(SIRp ), where f(x) represents the function mapping relationship, and the mapping relationship between the value of f(x) and x is determined by the noise power in the network and the radius of the average one-hop coverage of the network node; SIRp is determined by the network node The adopted channel codec scheme, modulation and demodulation scheme, and the data bit transmission error probability that the receiver can allow are determined; the sending node A starts timing and enters step a.6; a.3 The receiving node B uses the common code to receive and despread the RTS packet sent by the sending node A, and obtains the signal-to-noise ratio (SIRs) of the RTS packet through statistics, and takes out the user code of the source node in the RTS packet to update the user code selected by the receiving node B. user code; a.4 Compare the RTS packet signal-to-noise ratio SIRs obtained in step a.3 with the threshold signal-to-noise ratio SIRp predetermined by the network. If SIRs<SIRp, the receiving node B does not send a clear-to-send CTS packet to the sending node A, and enters the step a.3; otherwise, the receiving node B calculates the redundant signal-to-noise ratio SIRa, SIRa=SIRs-SIRp, and according to the value PT of the transmitting power field in the RTS packet described in step a.2, determines that the transmitting power of the receiving node B is PT-f(SIRa); a.5 The receiving node B sends a CTS packet to the sending node A with the transmit power PT-f(SIRa) determined in step a.4; the CTS packet includes a type field, a source address field, a target address field, and a transmit power field, wherein Fill in the identification code indicating that the packet is a CTS packet in the type field, fill in the address of receiving node B in the source address field, fill in the address of sending node A in the target address field, fill in the receiving node B determined in step a.5 in the transmit power field The transmit power value PT-f(SIRa); a.6 If sending node A receives the CTS packet sent by receiving node B within Tt time, then enter step a.7, otherwise, sending node A enters step a.9; a.7 Sending node A determines the transmit power used by sending node A when sending data packets to receiving node B subsequently according to the value of the transmit power field in the CTS packet received in step a.6, the value of the transmit power Get the value of the transmit power field in the CTS packet; a.8 The sending node A uses the user code of the node A and the transmission power determined in step a.7 to send the data packet to the receiving node B, and the receiving node B uses the user code determined in step a.3 to receive and despread the data packet, Then send an acknowledgment ACK packet to the sending node A; a.9 Sending node A increases the transmission power by dt, and increases the value of the transmission power field in the RTS packet by dt. When the cumulative number of repeated transmissions is less than the maximum allowable number of repeated transmissions Rm, and the transmission power is less than or equal to the maximum allowable transmission power, send Node A resends an RTS packet to receiving node B with the transmission power after dt is increased, and returns to step a.6, otherwise, treat receiving node B as unreachable; a.10 The receiving node B is unreachable, the sending node A adds the data packet to the queue of the node waiting to send the packet, and re-enters step a.1; When the network node has no data packets to send, the access method is: b.1 Network node A uses the common code to receive and despread the control packet, and obtains the signal-to-noise ratio of the received control packet as SIRs through statistics; judges whether the received control packet is an RTS packet according to the value of the type field in the received control packet, if If the received control packet is an RTS packet, proceed to step b.2, otherwise, network node A re-executes step b.1; b.2 Determine whether the address of the network node A is the same as the target address in the RTS packet. If not, the network node A determines that the channel is busy, and after a delay of Δt, re-execute step b.1; otherwise, take out the RTS packet The user code of the source node updates the user code of node A in this network; b.3 Compare the receiving control packet signal-to-noise ratio SIRs obtained in step b.1 with the threshold signal-to-noise ratio SIRp predetermined by the network. The allowable data bit transmission error probability is determined; if SIRs<SIRp, then network node A enters step b.1; otherwise, network node A calculates the redundant signal-to-noise ratio SIRa, SIRa=SIRs-SIRp, and receives according to step b.1 The value PT of the transmission power field in the control packet determines that the transmission power of the network node A is PT-f(SIRa), f(x) represents the function mapping relationship, and the mapping relationship between the value of f(x) and x is given by The noise power in the network and the radius of the average one-hop coverage of network nodes are determined; b.4 Send CTS packet to the node sending RTS packet in step b.1 with the node transmission power PT-f(SIRa) determined in step b.3; the source address field of CTS packet is filled with the address of network node A, and the destination address Field fills in the address of the node that sends RTS packet in step b.1, transmits the power field and fills in the node transmission power value PT-f (SIRa) that step b.3 determines; b.5 After the node sending the RTS packet in step b.1 receives the CTS packet, it uses the user code of the node and the transmit power determined by the transmit power field in the CTS packet to send a data packet to the network node A, and the network node A receives After the data packet, send an ACK packet to the node that sent the RTS packet in step b.1. 2. the controllable distributed CDMA network media access control method of power according to claim 1, it is characterized in that the spreading code configuration method that adopts is: network configures Ns spreading codes altogether, wherein one spreading code uses It is used as a public spreading code, referred to as a common code, which is used to send control packets and is known to each network node; the remaining Ns-1 spreading codes are used as user spreading codes, referred to as user codes, for Send data packets; the network node configures the spreading code as a common code during initialization, and at the same time randomly selects and sets a user code as the initial user code of the node, and the network node can update the user code of the node as needed; the network node updates the node The rule of the user code is: if the received control packet is an RTS packet, and the address of the node is the same as the address of the target node in the RTS packet, then update the user code of the node to the user code of the source node in the RTS packet; otherwise, the node The user code remains the initial user code of the node.

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