System and method for microwave traffic routing

A radio communication system has a primary communication pathway and a secondary communication pathway. When the primary communication pathway is implemented by a microwave radio link, it is susceptible to poor performance under adverse weather conditions. A system evaluates the available data bandwidth under adverse conditions and provides control instructions to a data switch to reduce the data flow to the primary communication pathway. In addition, the data switch may receive priority control data to prioritize data queues to the primary communication pathway and the secondary communication pathway in accordance with the received instructions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed generally to a communication system and, more particularly, to a system and method for routing traffic in a communication system having a microwave link.

2. Description of the Related Art

Wireless communication systems have become commonplace. A conventional wireless communication system comprises a number of distributed access points, such as base stations. Subscribers communicate bi-directionally with the base stations. The data at the distributed access points must be delivered to a centralized point-of-presence, such as a mobile switching center (MSC). The communication links between the distributed access points (e.g., the base stations) and the centralized access point (e.g., the MSC) is referred to as a backhaul.

The backhaul communication pathway may be implemented using a variety of known technologies. For example, the base station may be coupled to the MSC using a wire or optical fiber. Microwave communication links are also used to implement the backhaul. Many communication systems will provide multiple different communication pathways to implement the backhaul. For example, a base station may be coupled to the MSC using a microwave link and a copper wire.

An advantage of a microwave backhaul link is that it does not require a physical connection between the base station and the MSC. Furthermore, microwave communication links are well-known and readily available in the commercial marketplace. A disadvantage of a microwave link is that it is susceptible to the effects of adverse weather. For example, the water droplets in rain cause a significant adverse impact on the microwave link. Thus, bad weather essentially reduces the available data bandwidth on a microwave link.

In a system with multiple backhaul links, a data switch couples the distributed access point (e.g., the base station) with the MSC. Such data switches are commercially available and include queuing algorithms to maintain priority in communications across the backhaul link.

Unfortunately, the conventional data switch has no information regarding the available data bandwidth in a microwave link nor does the switch have any information regarding the quality of the microwave link. When adverse weather decreases the available data bandwidth in the microwave link or adversely affects the quality of the microwave link, the switch detects problems in a communication link, such as a detection of transmission errors and the requirement for retransmission of data, and simply shuts down the microwave link and transfers all traffic to a secondary backhaul link regardless of bandwidth availability on the microwave backhaul link. Therefore, it can be appreciated that there is a significant need for a system and method that maintains operation of a microwave link even in the face of adverse weather. The present disclosure provides this, and other advantages, as will be apparent from the following detailed description and accompanying figures.

DETAILED DESCRIPTION OF THE INVENTION

Wireless communication systems have evolved from simple cell sites with limited coverage area for voice communication to complex networks with extensive coverage and high speed broadband communication capabilities for voice, data, video, and the like. As the wireless communication networks continue to evolve, more sophisticated forms of communication are required.

The present disclosure is directed to techniques for apportioning data among a primary and a secondary data pathway. As discussed above, a conventional data switch transmits data on either a primary pathway or a secondary pathway. If the primary pathway is implemented by a microwave communication link, there is a potential for a degradation of signal quality and a reduction in bandwidth in adverse weather conditions. The conventional switch receives error data and detects an increase in errors for data being transmitted via the primary pathway. The conventional switch responds by terminating all communication to the primary pathway and switching data to the secondary pathway.

In contrast, the present disclosure describes techniques by which a microwave radio can communicate control information to a data switch to indicate that, while bandwidth is reduced as a result of adverse weather conditions, there is still some bandwidth available for transmission of data on the primary pathway. Thus, the data switch may re-apportion data flow between the primary and secondary pathways, but will not totally shut down the primary pathway as is done in conventional switches.

The techniques described herein may be implemented as a system100, illustrated in an example embodiment inFIG. 1.FIG. 1illustrates base stations102-108. The base station102is coupled to user equipment (UE)110-112via wireless communication links114-116, respectively. Those skilled in the art will appreciate that the UE110-112are representative of a broad variety of wireless devices that may communicate with the base station102. For example, the UE110-112could be conventional analog cell phones, such as advance mobile phone system (AMPS) devices, personal communication system (PCS) devices, personal digital assistant (PDA) devices, voice over internet protocol (VoIP) devices, personal computers (PC), or the like. The use of these various communication devices in a wireless setting is well known and need not be described in greater detail herein. Those skilled in the art will appreciate that the base stations illustrated inFIG. 1would typically have many UEs coupled to each base station. However, for the sake of clarity,FIG. 1illustrates only four base stations (i.e., the base stations102-108) and only two UE (i.e., the UE110-112) coupled to a single base station.

The present disclosure is directed to communication between the base stations102-108and a central point-of-presence. In the system100illustrated inFIG. 1, a mobile switching office or mobile switching center (MSC)120receives communication from the various base stations using communication links commonly referred to as a backhaul. The present disclosure is directed to the backhaul communication rather than the communication links114-116with the UE110-112, respectively. Accordingly, those skilled in the art will appreciate that the UE110-112may be implemented using any known form of wireless communication and multiple access protocols. For example, the UE110-112could be implemented using GSM, CDMA, 3G, 4G, WiMax, and the like. Each of these various communication protocols are known in the art and need not be described in greater detail herein. In addition, each of these communication protocols may use various techniques for multiple user access. For example, the UE110-112may utilize time-division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA) or the like. The present disclosure is applicable to any form of UE and equally applicable to any communication protocol and any multiple access technique to provide the communication links114-116between the base station102and the UE110-112, respectively. Accordingly, the system100is not limited to any specific communication process between the base station102and the UE110-112.

In the illustration ofFIG. 1, the system100is implemented in a ring architecture122in which some base stations communicate with the MSC120via other base stations in the same ring. For clarity, the ring architecture122illustrated inFIG. 1includes only the four base stations102-108. Those skilled in the art will appreciate that a ring architecture can include greater or fewer than the four base stations102-108. For example, the ring architecture may include only three base stations or may include 20-30 base stations. The specific example illustrated inFIG. 1is an exemplary embodiment to illustrate communications via multiple pathways. In the ring122illustrated inFIG. 1, MSC120is coupled to the ring between the base stations106-108. Thus, the base stations106-108may communicate directly with the MSC120via their respective communication links.

The base stations102-104must communicate with the MSC120via either the base station106or the base station108. The base station102can communicate with the MSC120via a primary communication pathway124or a secondary communication pathway126. As illustrated inFIG. 1, the primary pathway124allows communication between the base station102and the MSC120via the base station104and the base station106. The secondary pathway126allows communication between the base station102and the MSC120via the base station108. The present disclosure is directed to methods for microwave traffic routing and, therefore, is broadly applicable to a microwave communication link. The following discussion will focus on the base station102and the primary pathway124, and the secondary pathway126. For purposes of the present discussion, it will be assumed that the primary pathway124is implemented as a microwave communication link.

While the ring architecture122illustrated inFIG. 1provides alternate communication pathways for each base station, the techniques of the present disclosure do not require such an architecture. For example,FIG. 2illustrates the base station102and the MSC120in a different architecture. In the architecture ofFIG. 2, the primary pathway124and the secondary pathway126both couple the base station102directly with the MSC120. In the example ofFIG. 2, the primary pathway124is implemented as a microwave communication link. The secondary pathway126may be implemented with a hard wire, fiberoptic link, wireless link (e.g., a microwave link or other radio frequency link), or the like. Thus, the system100is not limited only to the ring architecture122ofFIG. 1.

FIG. 3is a functional block diagram of the base station102and illustrates the UE110-112. The base station102includes a base station cellular radio system130that establishes and maintains the communication links114-116with the UE110-112, respectively. The base station cellular radio system130typically includes one or more transmitter/receiver pairs, which may be implemented as transceivers as well as associated amplifiers and antenna. In many implementations, the base station102may have multiple sectors of geographic coverage wherein each sector has a transmitter/receiver pair and antenna. For example, it is common for a base station to have three coverage sectors. The base station has a separate antenna for each coverage sector as well as a different radio transmitter/receiver pair for each sector. In some implementations, each radio transmitter/receiver pair operators at a different frequency. This depends on the specific communication protocol being implemented by the base station cellular radio system130. Those skilled in the art will appreciate that other variations, such as greater or fewer sectors, different radio frequency assignment patterns, different communication protocols, different multiple user access protocols and the like are all possible depending on the specific implementation of the base station cellular radio system130.

The base station cellular radio system130is coupled to a data switch132via a data link134. The data switch132is a commercial device available from a number of a different manufacturers. In a typical implementation, the data switch132organizes data received the data link134into a number a different queues based on the priority of a particular traffic flow. The operation of queuing algorithms and flow control by the data switch132is known in the art and will be described herein only as it relates to operational control of the data switch.

In a typical communication system, a base station controller (not shown) or similar network element controls operation of the base station102, including control of the base station cellular radio system. The base station102(and/or the base station controller) exchange network control information with the MSC120. Network control information is considered to be the highest priority communication since the entire system may fail in the event of a failure to transmit and/or receive this high priority data. This network control information is considered to be the highest priority communications that occurs in the system100and is thus given top priority for processing and transmission. Other forms of data, such as VoIP, video data, and the like are time-sensitive and jitter-sensitive and receive high priorities based on a particular quality of service (QoS) provided to a particular customer. Other communication traffic, such as web surfing, email, and the like are less time-sensitive. This type of traffic is often designated as “Best Efforts” traffic, meaning that the system100will route this type of data with its best possible efforts, but does not provide any guarantee such as may be provided with higher QoS traffic.

In addition to queuing algorithms implemented by the data switch132, the data switch has routing algorithms to control outgoing data and direct it to the primary pathway124or the secondary pathway126. As discussed above, a conventional switch routes all data on the backhaul link implemented by the microwave unless a problem is detected with microwave transmission. In the event of adverse weather, the data bandwidth available via the microwave link is reduced. In addition, the quality of the signal may also be reduced. The conventional data switch interprets these problems as a failure of the primary pathway and automatically switches to the secondary pathway irrespective of any available bandwidth that may still be provided by the primary pathway.

In contrast, elements of the base station102detect the reduced the data bandwidth available on the primary pathway126and sends a control message to the data switch132indicating the available bandwidth on the primary pathway. The data switch132limits the data flow to the primary pathway124to meet the new constraints imposed by the limited data bandwidth. At the same time, traffic flow may be increased to the secondary pathway126while data flow is still maintained, at some level, to the primary pathway124. Thus, the data switch132advantageously maintains some data flow to the primary pathway124and provides better overall utilization of communication capabilities within the system100than would be possible if the data switch simply cut off all communication to the primary pathway as is done in conventional data switches. Operational details of the base station102are provided below.

As described above with respect toFIG. 3, the primary pathway124is implemented using a microwave communication link. While the secondary pathway126may be implemented as a hard wire cable link, fiberoptic link, wireless link (e.g., a microwave link or other radio frequency link) or a combination of the above. The microwave communication on the primary pathway124is implemented using a microwave radio system136. As will be described in greater detail below, the microwave radio system136communicates control information to the data switch132via a control link138. The control link138provides data bandwidth and other information to the data switch132that allows the data switch to reduce data flow to the primary pathway if necessary, but does not cause the data switch to completely shut down the primary pathway124. The control link138also carries information regarding the priority of data to be transmitted on the primary pathway124. This is especially important under adverse weather conditions where the primary pathway may have sufficient bandwidth to handle a certain type of data flow, but the information on the control link138instructs the data switch132to transfer communication traffic to the secondary pathway on the basis of traffic priority. This prioritization will also be discussed in greater detail below.

FIG. 4illustrates a functional block diagram of the microwave radio system136. The microwave radio system136includes a central processing unit150(CPU) and a memory152. The CPU150may be implemented as a conventional microprocessor, a digital signal processor, microcontroller, programmable-gate array, discrete circuitry, or the like. The microwave radio system136is not limited by the particular form of circuitry used to implement the CPU150.

Similarly, the memory152may be implemented as random access memory, read-only memory, programmable memory, flash memory, a combination of one or more of the above types of memory, or other similar data storage devices. In one embodiment, a portion of the memory152may be integrated into the CPU150. Thus, the microwave radio system136is not limited by the particular form of circuitry used to implement the memory152. In general, the memory152contains instructions and data that are executed by the CPU150.

The microwave radio system136may also include a data storage area154, such as a disk drive or the like. In one embodiment, the data storage area154may be part of the memory152. In one embodiment, the data storage area154may serve as a buffer for data awaiting transmission via the primary pathway124.

FIG. 4also illustrates a network interface controller (NIC)156. The NIC156may be a conventional communication interface, such as an Ethernet interface, IEEE 1394 interface, USB interface, or the like. The microwave radio system136is not limited by the specific form of the NIC156. The NIC156is coupled to the control link138to thereby establish communication between the microwave radio system136and the data switch132.

FIG. 4also illustrates a radio link evaluation processor158. As will be discussed in greater detail below, the radio link evaluation processor158collects data and evaluates the available data bandwidth and the quality of the primary pathway124. This information forms the basis of communication between the microwave radio system136and the data switch132that will allow some data to flow through the primary pathway124even under most adverse weather conditions.

FIG. 4also illustrates a microwave transmitter160and a microwave receiver162. In some implementations, the transmitter160and receiver162may share components and be implemented as a microwave transceiver164. The transceiver164is coupled to an antenna166. The antenna166may be implemented as a parabolic dish to provide greater signal gain and directivity. In addition, the operational frequencies of the transmitter160and receiver162may be controlled in accordance with conventional standards for microwave communication. Those skilled in the art will appreciate that the microwave radio system136typically communicates via line-of-sight. The primary pathway124may include one or more microwave repeaters (not shown) if line-of-sight communication is not available between the base station102and the base station104(seeFIG. 1). The microwave transceiver164and antenna166are commercial devices whose operation is well understood. Accordingly, the operation of the microwave transceiver164and antenna166need not be described in greater detail herein.

The various components described above area coupled together by a bus system168, which may include a data bus, address bus, power bus, control bus, and the like. For the sake of clarity, those various buses are illustrated herein as the bus system168.

Those skilled in the art will appreciate that some elements illustrated in the functional block diagram ofFIG. 4may be implemented as a series of instructions stored in the memory152and executed by the CPU150. For example, the radio link evaluation processor158may be implemented as a series of instructions and data stored in the memory152and executed by the CPU150. This element is illustrated as a separate block in the functional block diagram ofFIG. 4because it performs a separate function.

In normal operation, the microwave radio system136typically has 50 megahertz (MHz) of radio frequency (RF) bandwidth and can provide a data bandwidth or data delivery rate of at least 200 megabits per second (Mbps). However, this is subject to weather conditions. The microwave radio system136communicates using quadrature amplitude modulation (QAM). In good weather, a complex QAM modulation may be used to provide greater data throughput for a given RF bandwidth. For example, in good weather conditions, the microwave radio system will use 256 QAM modulation to provide a data delivery rate of at least 200 Mbps. That is, the complex modulation provided by 256 QAM allows more data bits per unit of RF bandwidth than other forms of modulation. As weather conditions deteriorate, the microwave radio system136will reduce the modulation rate to provide more robust transmission with greater error recovery capability.

When adverse weather conditions are present, it is not the RF bandwidth (e.g., 50 MHz) that is reduced, but the data bandwidth or delivery rate. This process, known as adaptive modulation, allows the microwave radio system136to use a complex modulation scheme when conditions are good to deliver the maximum data rate. Under adverse conditions, lower modulation forms (e.g., 128 QAM) may be used that provide a more robust signal, with greater error detection/correction, but at a lower data bandwidth. Those skilled in the art will appreciate that these lower forms of modulation require greater RF bandwidth per data bit resulting in a lower data delivery rate. Under more adverse weather conditions, the adaptive modulation rate may be reduced to a lower form of modulation referred to as quadrature phase shift keying (QPSK). Operation of the microwave radio system136using QPSK may result in a data bandwidth as low as 10 Mbps even though the microwave radio system still operates at a 50 MHz RF bandwidth.

Other measurements may also be derived by the system100to measure the quality of the primary pathway124. In the ring architecture122illustrated inFIG. 1, the primary pathway124of the base station102provides a communication link with the base station104. If this primary pathway124is implemented by a microwave link, (i.e., the microwave radio system136ofFIG. 4), a microwave radio system (not shown) associated with the base station104transmits certain data to the base station102related to the quality of the signal link provided by the primary pathway124. The microwave radio system in the base station104operates in a manner similar or identical to that of the microwave radio system136in the base station102. The microwave radio system associated with the base station104provides a signal to noise (S:N) ratio to the microwave radio system136. The S:N ratio may be delivered in the form of a bit error rate (BER), as is known in the industry. Under normal operating conditions, the BER may typically be 1×10−6. This means that approximately one in a million bits is received in error. However, under adverse conditions, the BER may be reduced to 1×10−4or 1×10−3. Thus, the BER provides a measure of the quality of the primary pathway independent of the actual data bandwidth availability.

In addition to the BER, the microwave radio system (not shown) associated with the base station104provides a signal strength measurement in the form of a received signal level (RSL) or a received signal strength index (RSSI). Under normal operating conditions, an RSSI of −35 dBm to −70 dBm is typically sufficient for a good quality connection. As the signal level drops below −70 dBm, the receiver may be unable to operate satisfactorily and the error rate (e.g., the BER) may increase as the S:N ratio decreases.

Those skilled in the art will appreciate that the modulation level, the RSSI, and the BER are separate measurements, but are not totally independent. For example, a lower signal level will result in a lower RSSI. A lower RSSI by itself may not result in an increased BER so long as the RSSI is above some minimum threshold. However, if the RSSI falls to an unsatisfactory level, the BER will increase. The microwave radio system136utilizes these factors in selecting an adaptive modulation level. For example, operation at a selected amplitude modulation level may be satisfactory until the BER falls below some user-selected threshold. At this threshold, it is considered that the error rate is unacceptable. At that point, the microwave radio system136may switch to a lower modulation level. At the lower modulation level, the BER would be expected to rise to a satisfactory level. The conventional data switch has no knowledge of the modulation level selected by the microwave radio system nor does it have any knowledge of the RSSI or BER. The conventional data switch merely knows that data is not being delivered as quickly as it is being sent and the conventional data switch totally cuts data delivery to the primary pathway and delivers all data to the secondary pathway.

In contrast, the radio link evaluation processor158analyzes the adaptive modulation level, the BER, and the RSSI to determine an effective data delivery rate and provides instructions, via the control link138, to the data switch132. The instructions on the control link138include data related to the available data delivery rate, which may be referred to as the data bandwidth, and may further provide queuing instructions indicating which type of data should be delivered to the primary pathway124and the secondary pathway126. The queuing priority will be discussed in greater detail below.

FIG. 5is a functional block diagram of the data switch132. The data switch132contains data queuing logic180that receives incoming data and places the incoming data in one of a plurality of queues182based on priorities assigned to the incoming data traffic. The data switch132illustrated inFIG. 5contains eight data queues182. By convention, Queue8is designated to handle the highest priority traffic through the data switch132while the Queue1is designated to carry the lowest priority data traffic in the data switch. As discussed above, the highest priority data traffic is typically network control traffic exchanged between network elements, such as the base stations102-108and the MSC120and/or a base station controller (not shown). Those skilled in the art will appreciate that no communication network will operate without the exchange of such control/management data. Accordingly, this data is designated as the highest priority data and routed to Queue8. Other time-sensitive traffic, such as VoIP traffic, video conferencing data and the like is generally designated as high priority traffic based on the quality of service (QoS) level purchased by a subscriber. Other types of data that may be time-sensitive and/or jitter-sensitive, may be classified in high priority queues, such as Queue6and Queue7. Other lower-priority traffic, sometimes designated as Best Effort (BE) traffic is assigned to lower-priority queues, such as Queue3-Queue1. The data queuing logic180identifies the type of data flow and assigns it to one of the queues182based on priority.

The data switch132also includes data switching logic184. The data switching logic184is coupled to the output of the queues182. The data switching logic184routes data to the primary pathway124and/or the secondary pathway126. As noted above, a conventional data switch routes all data to the primary pathway, when functional. Under normal operations, all data is routed to the primary pathway by the conventional data switch. If data transmission errors occur, such as may happen during adverse weather conditions, the conventional data switch merely detects that data is not flowing properly to the primary pathway. The response of the conventional data switch is to shut down the primary pathway and switch all data to the secondary pathway regardless of priority and regardless of available data bandwidth.

In contrast, the data switching logic184will route data flows to both the primary pathway124and the secondary pathway126. Under normal operating conditions, the data switching logic184routes all data, regardless of priority, to the primary pathway124via the microwave radio system136.

In an alternative embodiment, the data switching logic184may route a portion of data to the secondary pathway126even under normal operating conditions. For example, the system100may determine that the traffic load on the primary pathway124is heavy while traffic on the secondary pathway126is relatively light. The system100may achieve a form of load balancing by transferring some of the data load from the primary pathway124to the secondary pathway126even when adverse weather is not affecting the primary pathway124.

In adverse weather conditions, the microwave radio system136determines that the primary pathway124is not capable of handling the normal data bandwidth. The microwave radio system136informs the data switch132, via the control link138, that a limited data bandwidth is available using the primary pathway124. The data switching logic184apportions data from the queues182to the primary pathway124and to the secondary pathway126.

In addition to data bandwidth information provided to the data switch132on the control link138, the microwave radio system136provides queuing instructions used by the data queuing logic180and the data switching logic184. In response to control information on the control link138, the data switching logic184will route the data from the various data queues182in accordance with instructions from the microwave radio system136. For example, the available bandwidth on the primary pathway124may be sufficient to carry the high priority data from Queue8. However, based on other factors, such as the RSSI and BER, the control information from the microwave radio system136may instruct the data switch to route this high priority data to the secondary pathway126regardless of the data bandwidth availability. On the other hand, the limited data bandwidth on the primary pathway124may support lower priority traffic, such as BE traffic. For example, web-based traffic or email traffic may be routed over the primary pathway124in order to maximize overall resources of the system100.

FIG. 6is a flowchart illustrating the operation of the system100illustrated by either of the example architectures inFIGS. 1 and 2. At a start200, the communication network is operational. At step202, the radio link evaluation processor158(seeFIG. 4) of the microwave radio system136receives radio measurement data. As discussed in detail above, the radio measurement data may include the selected modulation level, the RSSI, and the BER. These data parameters may be used to provide an indication of data bandwidth availability on the primary pathway124and the quality of the radio link in the primary pathway.

In step204, the radio link evaluation processor158determines the available data bandwidth. As discussed above, the available data bandwidth may be determined on the basis of RF bandwidth and the selected modulation level.

In step206, the radio link evaluation processor158determines the queuing priorities. This may include a determination of specific queues that will be routed on the primary pathway124and/or the secondary pathway126. Alternatively, the queuing priorities may be based on a type of traffic flow. For example, the queuing priorities may determine that BE traffic may be routed on the primary pathway124even during adverse weather conditions with limited data bandwidth availability. Those skilled in the art will appreciate that BE traffic is often carried on multiple ones of the queues182. Thus, queuing priorities may be designated on the basis of traffic type rather than specific queue numbers.

In step208, the microwave radio system136transmits one or more messages to the switch132regarding data bandwidth availability and queuing instructions.

In response to the messaging from the microwave radio system136, the data switch132adjusts the data flow to the primary pathway124on the basis of data bandwidth availability. In addition, the data switch132routes data on the primary pathway124and the secondary pathway126. As discussed above, the response to the queuing instructions may be on the basis of uniquely identified data queues (e.g., Queue8) or on the basis of traffic type (e.g., BE traffic). Those skilled in the art will appreciate that step208need not be executed if there are no changes in the operation of the microwave radio system136. For example, if the microwave radio system136is operating in good weather conditions and utilizing the maximum data bandwidth, there is no need to send continuous messages to the data switch132. This would essentially be continuously telling the data switch to keep doing what it is already doing. However, if conditions change, the microwave radio system136may send a message in step208instructing the data switch136to offer its operating parameters in accordance with the instructions.

Following the execution of step208, if a message is sent at step208, the operation returns to step202to again receive radio measurement data. Thus, the microwave radio system continuously receives data and performs the analysis illustrated inFIG. 6to constantly monitor conditions in the primary pathway126.

At present, there is no standard communication protocol for the exchange of control information between the microwave radio system136and the data switch132. However, there are existing communication protocols that may be capable of modification to accomplish the communication between the microwave radio system and the data switch. For example, IEEE 802.1 defines communications standards for sharing information within a network. IEEE 802.1q defines an encapsulation protocol that is used for virtual local area network (VLAN) tagging. Such communication protocols can be extended or expanded to include data exchanges between the microwave radio system136and the data switch132.FIG. 7illustrates an example message exchange. At220, the microwave radio system136transmits a bandwidth availability message to the data switch132. The data switch132may respond with an optional bandwidth acknowledgement (BW_ACK) message222. The microwave radio system136may send queuing instructions224. The data switch132may optionally respond with a queuing acknowledgement (QUE_ACK)226. Those skilled in the art will appreciate that a single message may be transmitted that contains both bandwidth availability and queuing instructions.

Other communication messages may also be exchanged between the microwave radio system136and the data switch132. For example, the microwave radio system may periodically, at a predetermined interval, send a radio time-out message228. The radio time-out message228provides positive communication between the microwave radio system136and the data switch132to show that the communication link138is still active. Such a message may be important at times when there are no changes in the bandwidth availability in queuing instructions. In this manner, the base station102can confirm proper operation of the communication link138. The data switch132may respond to the radio time-out message228with a time-out acknowledgement message230. Other forms of housekeeping messages may also be exchanged between the microwave radio system136and the data switch132.