Abstract:
The present invention provides techniques for responding to overlapping conditions in wireless communications networks include receiving data transmissions from a transmitting device across a wireless communications network. These data transmissions correspond to a connection with the transmitting device and occur within a reserved portion of a communications resource. An interference condition is detected that includes an allocation of the communications resource for a neighboring device that overlaps with the reserved portion. Based on this detection, the method sends a notification to the transmitting device, the notification indicating the presence of overlapping transmissions in the reserved portion of the communications resource.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to wireless communications. More particularly, the present invention relates to techniques for reducing interference of transmissions in wireless communications networks.  
       BACKGROUND OF THE INVENTION  
       [0002]     Short-range wireless proximity networks typically involve devices that have a communications range of one hundred meters or less. To provide communications over long distances, these proximity networks often interface with other networks. For example, short-range networks may interface with cellular networks, wireline telecommunications networks, and the Internet.  
         [0003]     A high rate physical layer (PHY) standard is currently being selected for IEEE 802.15.3a. The existing IEEE 802.15.3 media access control layer (MAC) is supposed to be used as much as possible with the selected PHY. Currently, there are two remaining PHY candidates. One of these candidates is based on frequency hopping application of orthogonal frequency division multiplexing (OFDM). The other candidate is based on M-ary Binary offset Keying. The OFDM proposal is called Multiband OFDM (MBO). Moreover, in order to further develop the OFDM proposal outside of the IEEE, a new alliance has been formed called the MultiBand OFDM Alliance (MBOA).  
         [0004]     MBO utilizes OFDM modulation and frequency hopping. MBO frequency hopping may involve the transmission of each of the OFDM symbols at various frequencies according to pre-defined codes, such as Time Frequency Codes (TFCs). Time Frequency Codes can be used to spread interleaved information bits across a larger frequency band.  
         [0005]     Presently, there is an interest within the MBOA to create a Medium Access Control (MAC) layer that would be used with the OFDM physical layer instead of the IEEE 802.15.3 MAC layer. A current version of the MBOA MAC involves a group of wireless communications devices (referred to as a beaconing group) that are capable of communicating with each other. The timing of beaconing groups is based on a repeating pattern of “superframes” in which the devices may be allocated communications resources.  
         [0006]     MAC layers govern the exchange among devices of transmissions called frames. A MAC frame may have various portions. Examples of such portions include frame headers and frame bodies. A frame body includes a payload containing data associated with higher protocol layers, such as user applications. Examples of such user applications include web browsers, e-mail applications, messaging applications, and the like.  
         [0007]     In addition, MAC layers govern the allocation of resources. For instance, each device requires an allocated portion of the available communication bandwidth to transmit frames. The current MBOA MAC proposal provides for the allocation of resources to be performed through communications referred to as beacons. Beacons are transmissions that devices use to convey non-payload information. Each device in a beaconing group is assigned a portion of bandwidth to transmit beacons.  
         [0008]     Such transmissions allow the MBOA MAC to operate according to a distributed control approach, in which multiple devices share MAC layer responsibilities. A channel access mechanism, referred to as the Distributed Reservation Protocol (DRP) is an example of such shared responsibility. DRP includes basic tools for establishing and terminating a unidirectional connection between two or more devices.  
         [0009]     In a distributed network, a device making a reservation for a connection with another device may not be aware of the reservations of the devices around the other device. Therefore, the MBOA MAC provides for an Availability Information Element (AIE), which indicates the usage of communications resources from other device&#39;s perspective.  
         [0010]     The current MBOA MAC Specification (version 0.62, September 2004) only requires an AIE to be sent in limited circumstances involving establishment of a new connection. Otherwise, it is optional to send the AIE. However, the mobility of devices may cause previously acceptable resource allocations to become ones that cause significant interference.  
         [0011]     There has been a proposal for devices to transmit AIEs in every superframe. Although such an approach would reduce interference, it would also cause several problems. Such problems include the overloading of bandwidth allocated for beacon transmissions. This overloading would obstruct the sending of other important beacon transmissions. Accordingly, techniques are needed for the reduction of interference that do not waste communications resources.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention provides techniques for responding to overlapping conditions in wireless communications networks. For example, a method of the present invention receives data transmissions from a transmitting device across a wireless communications network. These data transmissions correspond to a connection with the transmitting device and occur within a reserved portion of a communications resource. The method further detects an interference condition that includes an allocation of the communications resource for a neighboring device overlapping with the reserved portion. Based on this detection, the method sends a notification to the transmitting device, the notification indicating the presence of overlapping transmissions in the reserved portion of the communications resource.  
         [0013]     In addition, the present invention provides a computer program product comprising program code to enable a processor to perform, for example, the features of the method.  
         [0014]     An apparatus of the present invention includes a receiver, a controller, and a transmitter. The receiver receives data transmissions from a transmitting device across a wireless communications network. These data transmissions correspond to a connection with the transmitting device and occur within a reserved portion of a communications resource. The controller detects an interference condition that includes an allocation of the communications resource for a neighboring device that overlaps with the reserved portion. The transmitter sends a notification to the transmitting device that indicates the presence of overlapping transmissions in the reserved portion of the communications resource.  
         [0015]     In addition, the present invention provides an apparatus having a transmitter, a receiver, a memory and a processor. The receiver receives data transmissions from a transmitting device across a wireless communications network that corresponds to a connection with the transmitting device and occurring within a reserved portion of a communications resource. The memory stores instructions for the processor to detect an interference condition that includes an allocation of the communications resource for a neighboring device that overlaps with the reserved portion. The transmitter sends a notification to the transmitting device, the notification indicating the presence of overlapping transmissions in the reserved portion of the communications resource.  
         [0016]     Additionally, the interference condition may further include the allocation of the communications resource for the neighboring device having a higher priority than the connection with the transmitting device. Also, the interference condition may further include the allocation of the communications resource for the neighboring device having an acknowledgment setting.  
         [0017]     The notifications sent to the transmitting device may be in the form of an availability information element (AIE) and or a modified distributed reservation protocol information element (DRP IE)  
         [0018]     Further features and advantages of the present invention will become apparent from the following description and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number. The present invention will be described with reference to the accompanying drawings, wherein:  
         [0020]      FIG. 1  is a diagram of an exemplary operational environment;  
         [0021]      FIG. 2  is a diagram showing an exemplary MBOA superframe format;  
         [0022]      FIGS. 3A and 3B  are diagrams of an exemplary communications scenario;  
         [0023]      FIGS. 4A and 4B  are diagrams showing an exemplary resource allocations for the connections of a wireless communications network;  
         [0024]      FIG. 5  is a flowchart of a device operation, according to an embodiment of the present invention;  
         [0025]      FIG. 6  is a flowchart of a device operation, according to a further embodiment of the present invention;  
         [0026]      FIG. 7  is a block diagram of an exemplary wireless communications device architecture according to an embodiment of the present invention; and  
         [0027]      FIG. 8  is a block diagram of an exemplary implementation of a wireless communications device according to an embodiment of the present invention; 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     I. OPERATIONAL ENVIRONMENT  
       [0028]     Before describing the invention in detail, it is first helpful to describe an environment in which the present invention may be employed. Accordingly,  FIG. 1  is a diagram of an exemplary operational environment. This environment includes multiple beaconing groups  101 , each having a plurality of devices  102 . For instance,  FIG. 1  shows a beaconing group  101   a,  which includes member devices (DEVs)  102   a - e.    FIG. 1  also shows a beaconing group  101   b,  which includes DEVs  102   f,    102   g,  and  102   h.    
         [0029]     In beaconing group  101   a,  each of DEVs  102   a - d  may communicate with DEV  102   e  across a corresponding link  120 . For instance,  FIG. 1  shows DEVs  102   a  communicating with DEV  102   e  across a link  120   a.  In addition, in beaconing group  101   a,  each of devices  102   a - e  may communicate with each other directly. For instance,  FIG. 1  shows DEVs  102   c  and  102   d  communicating via a direct link  122   a.    
         [0030]     In beaconing group  101   b,  each of DEVs  102   f  and  102   g  may communicate with DEV  102   h  across a corresponding link  120 . For instance, DEV  102   f  communicates with DEV  102   h  across a link  120   f,  while DEV  102   g  communicates with DEV  102   h  across a link  120   g.  DEVs  102   f  and  102   g  in beaconing group  101   b  may also communicate with each other. For example,  FIG. 1  shows DEVs  102   f  and  102   g  communicating across a link  122   b.    
         [0031]     Each of links  122  and  120  may employ various frequency hopping patterns. These patterns may include, for example, one or more Time Frequency Codes (TFCs). In embodiments of the present invention, each beaconing group  101  employs a particular frequency hopping pattern. These patterns may either be the same or different.  
         [0032]     Transmissions of beaconing groups  101   a  and  101   b  are each based on a repeating pattern called a superframe. Accordingly,  FIG. 2  is a diagram showing an exemplary MBOA superframe format. In particular,  FIG. 2  shows a frame format having superframes  202   a,    202   b,  and  202   c.  As shown in  FIG. 2 , superframe  202   b  immediately follows superframe  202   a,  and superframe  202   c  immediately follows superframe  202   b.    
         [0033]     Each superframe  202  includes a beacon period  204  and a data transfer period  206 . Beacon periods  204  convey transmissions from each of the active devices in the beaconing group. Accordingly, each beacon period  204  includes multiple beacon slots  207 , each corresponding to a particular device in the beaconing group. During these slots, the corresponding device may transmit various overhead or networking information.  
         [0034]     For instance, such information may be used to set resource allocations and to communicate management information for the beaconing group. In addition, according to the present invention, data transfer periods  206  may be used to transmit information regarding services and features (e.g., information services, applications, games, topologies, rates, security features, etc.) of devices within the beaconing group. The transmission of such information in beacon periods  204  may be in response to requests from devices, such as scanning devices.  
         [0035]     Data transfer period  206  is used for devices to communicate data according to, for example, frequency hopping techniques that employ OFDM and/or TFCs. For instance, data transfer periods  206  may support data communications across links  120  and  122 . In addition, devices (e.g., DEVs  102   a - e ) may use data transfer periods  206  to transmit control information, such as request messages to other devices. To facilitate the transmission of traffic, each DEV may be assigned a particular time slot within each data transfer period  206 . In the context of the MBOA MAC specification, these time slots are referred to as media access slots (MASs).  
         [0036]     A MAS is a period of time within data transfer period  206  in which two or more devices are protected from contention access by devices acknowledging the reservation. MASs may be allocated by a distributed protocol, such as the distributed reservation protocol (DRP).  
       II. INTERFERENCE SCENARIOS  
       [0037]      FIGS. 3A and 3B  are diagrams of an exemplary communications scenario in which several devices  302  participate in a short-range wireless communications network  300 , such as a beaconing group  101 . According to this scenario,  FIG. 3A  shows an initial arrangement of communications devices. A subsequent arrangement of these devices is shown in  FIG. 3B .  
         [0038]     Referring to  FIG. 3A , an initial set of conditions is shown. These initial conditions include a device  302   a  having a connection  350   a  with a device  302   b,  and a device  302   d  having a connection  350   b  with a device  302   e.  Traffic may be transferred across connections  350  in various ways. For example, an exemplary connection  350  includes a transmitting device (also referred to a sender) and a receiving device (also referred to as a receiver).  
         [0039]     The transmitting device sends data to the receiving device. In response, the receiving device may send information, such as acknowledgment messages to indicate reception of the transmitted data. The data and acknowledgment messages are transferred across an allocated portion of the available communications bandwidth, such as portion(s) of a superframe&#39;s data transfer period. As an illustrative example, device  302   a  is a sender and device  302   b  is a receiver for connection  350   a.  For connection  350   b,  device  302   e  is a sender and device  302   d  is a receiver.  
         [0040]     Each of devices  302  sends a beacon transmission during a beacon period, such as the beacon period of the superframe defined by the MBOA MAC. In addition, for each connection  350 , the participating devices  302  communicate data. These data communications may be, for example, during the data transmission portion of the superframe defined by the MBOA MAC.  
         [0041]     For purposes of illustration,  FIGS. 3A and 3B  include circles  304 , each representing spatial areas or locations. Devices that are within each particular circle  304  can receive each other&#39;s transmissions. For instance,  FIG. 3A  shows that devices  302   a  and  302   b  can receive each other&#39;s transmissions because they are within circle  304   a.  In a similar manner, devices  302   b  and  302   c  can receive each other&#39;s transmissions because the devices are both within circle  304   b.  Moreover, devices  302   c,    302   d,  and  302   e  can receive each other&#39;s transmissions because they are within circle  304   c.    
         [0042]     Due to the mobility of devices  302 , the communications environment may change, for example,  FIG. 3B  shows that device  302   d  has moved within circle  304   b.  Hence, device  302   d  can now receive communications from devices  302   b,    302   c,  and  302   e.  If the data communication schedules (e.g., DRP reservations) of connections  350   a  and  350   b  overlap in time, then communications across one or both of these connections will be subjected to severe interference.  
         [0043]      FIGS. 4A and 4B  show exemplary transmission time allocations (e.g., DRP schedule) for the connections of network  300 . These allocations are shown along a time axis  400  from the perspective of difference devices. In particular,  FIG. 4A  shows device perspectives at the initial conditions of  FIG. 3A , while  FIG. 4B  shows device perspectives at the subsequent conditions of  FIG. 3B .  
         [0044]     Referring to  FIG. 4A , an allocation perspective  402  for connection  350   a  is shown from the frame of reference of devices  302   a  and  302   b.  In addition,  FIG. 4A  shows an allocation perspective  404  for connection  350   b  from the frame of reference of devices  302   d  and  302   e.  It is apparent from these perspectives that the data communication allocations for connections  350   a  and  350   b  overlap in time. However, from the perspectives of devices  302   a,    302   b,    302   d,  and  302   e,  these allocations do not interfere with each other during the initial conditions of  FIG. 3A . This is because, for these initial conditions, devices  302   a  and  302   b  can not receive transmissions from devices  302   d  and  302   e,  and vice versa.  
         [0045]     However, for the subsequent conditions of  FIG. 3B , interference occurs. In particular,  FIG. 4B  shows an allocation perspective  406  from the frame of reference of device  302   a,  allocation perspective  408  and  410  from the frame of reference of devices  302   b  and  302   d,  as well as an allocation perspective  412  from the frame of reference of device  302   e.    
         [0046]     As shown by allocation perspectives  406  and  412 , transmissions (e.g., data) from device  302   b  to device  302   a  and from device  302   e  to device  302   d  are not interfered upon. However, allocation perspectives  408  and  410  show that transmissions from device  302   a  to device  302   b  and from device  302   e  to device  302   d  interfere with each other. However, due to the transmission environment of network  300 , devices  302   a  and  302   e  cannot identify the source of this interference (which may manifest itself as a reduction in throughput).  
         [0047]     In these situations, the devices that are prone to experiencing such interference can observe the overlapping allocation patterns and identify interference sources by receiving and processing the beacon transmissions from its neighboring devices. Accordingly, embodiments of the present invention provide for devices to communicate such interference sources to devices with which they share connections.  
       III. OPERATION  
       [0048]      FIG. 5  is a flowchart of an operation according to aspects of the present invention. This operation involves the interaction between a first device (the sender) and a second device (the receiver). In this operation, the receiver informs the sender if one or more interfering conditions exist. Based on such notifications, the interfering conditions can be removed. The operation of  FIG. 5  is described in the context of an MBOA network, such as a beaconing group  101  of  FIG. 1 . However, this operation may be used also in other contexts.  
         [0049]     As shown in  FIG. 5 , this operation includes a step  502  in which the sender and receiver participate in a wireless communications network, such as a beaconing group  101 . Accordingly, each of these devices is allocated non-payload communications resources, such as a beacon slot.  
         [0050]     In a step  503 , a connection is formed between the sender and the receiver. This connection includes an allocation of communication resources (e.g., one or more portions of a superframe&#39;s data transfer period). In an MBOA network, such allocations may be performed according to the distributed reservation protocol (DRP).  
         [0051]     DRP allows devices to make a reservation for a certain period of the data portion of the superframe. The establishment of a reservation is referred to as DRP negotiation. To establish and maintain the reservation (or connection) a device requesting a reservation (e.g., the sender) transmits a DRP information element (DRP IE) during its beacon slot. The other device(s) in the connection (e.g., the receiver) also transmits the DRP IE in its beacon slot. Both of these devices transmit the DRP IE in their respective beacon slots of each superframe during the existence of the reservation.  
         [0052]     In a step  504 , the sender transmits data to the receiver across the allocated communications resources (e.g., an existing DRP reservation). In embodiments, this step comprises receiving one or more data transmissions within the resources allocated to the connection between these devices. Upon the reception of such transmissions, the receiver may transmit corresponding acknowledgment messages to the sender in a step  506 . These data transmissions and acknowledgments may be in the form of OFDM signals.  
         [0053]     In a step  507 , the receiver monitors the non-payload transmissions (e.g., beacon transmissions) of any neighboring devices (i.e., devices from which the receiver can obtain transmissions). This monitoring includes receiving connection information for the neighboring device(s). Such connection information includes resources allocated to these devices for communications. In embodiments, this connection information is in the form of DRP IEs. As discussed above, a DRP IE defines which particular slots are being used by a beaconing device.  
         [0054]     Based on this monitoring, the receiver determines whether one or more reallocation conditions exist. Examples of such conditions are described below with reference to steps  508  through  512 .  
         [0055]      FIG. 5  shows that in step  508 , the receiver determines whether an allocation (e.g., a DRP reservation) of a neighboring device is overlapping with the resource allocations (e.g., DRP reservation) belonging to the receiver&#39;s connections. If so, operation proceeds to a step  510 . However, as alternatives,  FIG. 5  shows that operation may also proceed to either a step  512  or a step  516 , depending on the embodiment. Otherwise,  FIG. 5  shows that if there is no such overlapping, operation proceeds to a step  518 .  
         [0056]     In step  510 , the receiver determines whether the overlapping allocation of the neighboring device has a priority that is a higher than the receiver&#39;s connections. If so, then operation proceeds to step  512 . However, as an alternative,  FIG. 5  shows that operation may proceed to step  516 , depending on the embodiment. Otherwise, if overlapping allocation does not have a higher priority, operation proceeds to step  518 . It should also be noted, however, that in certain circumstances, such as in the case of an asymmetric communication link, the operation may (in embodiments) proceed to step  516 , even when the priority of the neighboring device is lower that the receiver&#39;s connections.  
         [0057]     In step  512 , the receiver determines whether the overlapping allocation (or reservation) of the neighboring device employs acknowledgments. For example, with reference to MBOA, step  512  may comprise determining whether the overlapping reservation employs an imm-ack or b-ack acknowledgment policy. As will be described below, such determinations may be obtained through information contained in an ACK policy field of a DRP IE. If such acknowledgments are employed, then operation proceeds to step  516 . Otherwise, step  518  is performed.  
         [0058]      FIG. 5  shows that step  516  is performed when the reallocation condition(s) of step  508 , and (in embodiments) steps  510  and/or  512  have been satisfied. In step  516 , the receiver and sender engage in communications to reallocate the receiver&#39;s communications resources. However,  FIG. 5  shows that a step  518  is performed when such conditions are not satisfied. In this step, the device foregoes performing reallocation actions.  
         [0059]     Performance of step  516  may be performed in various ways. One way involves the exchange of information through beacon transmissions. For instance, step  516  may comprise the receiver generating and transmitting an updated availability information element (AIE) during its beacon slot. Alternatively, step  516  may comprise the receiver generating and transmitting an updated and modified DRP IE. As a further alternative, step  516  may comprise the receiver generating and transmitting both an updated AIE and an updated and modified DRP IE. Also, the receiving device may receive a DRP IE from the transmitting device.  
       IV. AVAILABILITY AND DRP INFORMATION ELEMENTS  
       [0060]     According to the current MBOA MAC specification, the AIE is used by a device to indicate its view of the current utilization of MAS in the device&#39;s superframe. The format of the AIE is shown below in Table 1.  
                                 TABLE 1                           AIE Format                Octets: 32   1   1                       Availability Bitmap   Length (=x)   Element ID                      
 
         [0061]     As shown in Table 1, an AIE has an availability bitmap that is 256 bits long. Each of these bits corresponds to each MAS in the superframe. More particularly, each bit in the bitmap indicates the availability of the device for the corresponding MAS. For instance, a ‘0’ indicates that the device is available during the corresponding MAS, and a ‘1’ indicates that the device is not available during the corresponding MAS.  
         [0062]     Thus in step  516 , the sender may receive an AIE that indicates the existence of interfering allocations. Currently, the MBOA MAC specifies limited uses for the AIE. During a unicast DRP negotiation, a device is required respond to a requesting device with an AIE if the request cannot be completely accepted. This requirement may arise when the responding device is unable to accept the request due to conflict with other reservations. Otherwise, transmission of AIEs is optional. The transmitting device can make use of the receiver&#39;s AIE to make new reservations or modifications for the MAS slots that are free for the receiver. Accordingly, step  516 , may further comprise the receiving device sending a modified DRP IE in the next superframe.  
         [0063]     The format of a DRP of the MBOA MAC proposal is now described. Table 2, below, illustrates the format of a DRP IE.  
                                                                       TABLE 2                           Distributed Reservation Protocol Information Element Format            Octets: 2   2   2   3   1   1                    DRP   . . .   DRP   Destination/   DRP   Length   Element                   Source       Reser-       Reser-   DEVID   Control   (=x)   ID       vation 1       vation N                  
 
         [0064]     Table 2 shows that the DRP IE includes one or more DRP Reservation fields, each being 2 octets in length. The format of this field is shown below in Table 3.  
                             TABLE 3                           DRP Reservation field Format                Octets: 1   1                       DRP Length   DRP Offset                      
 
         [0065]     The DRP Offset field in Table 3 defines the starting time of the planned transmission. It shall be set to the slot number of the first reservation slot, which is defined relative to the beacon period start time (BPST). The DRP length field in Table 3 contains, in multiples of data slots, the duration of the reservation.  
         [0066]     Table 2 also shows that the DRP IE includes a three octet DRP control field. The format of this field is illustrated below in Table 4.  
                                         TABLE 4                           DRP Control Field Format            Bits: 8   5   5   4   1   1               Reserved   StreamID   Priority   Type   ACK   Tx/Rx                       Policy                  
 
         [0067]     In the DRP control field, the Tx/Rx bit is set to ‘0’ if the device is the sender of the planned transmission, and it is set to ‘1’ if the device is a receiver. This bit is only decoded if the reservation is of type Hard, or type Soft. The ACK (acknowledgment) policy bit of the DRP control field is set to ‘0’ for unicast reservations having a No-ACK policy and for multicast or broadcast reservations. However, this bit is set to ‘1’ for unicast reservations with Imm-ACK or B-ACK policies. The ACK policy bit is only decoded if the reservation is of type Hard or type Soft. The priority of the transmission is set by the DRP control field and can have a value between ‘0’ and ‘7’.  
         [0068]     The type field of the DRP control field indicates the type of the reservation and is encoded as shown below in Table 5.  
                         TABLE 5                       Types of DRP Reservations                                0000   Beacon Period       0001   Hard Reservation       0010   Soft Reservation       0011   Private Reservation       0100   Reserved       0101   Reserved       0110-1111   Reserved                  
 
         [0069]     The destination/Source DEVID field of the DRP IE is set to the receiver&#39;s device ID, multicast-group or broadcast when the device sending the DRP IE is the sender, and is the device ID of the sender when the device sending the DRP IE is a receiver. The DEVID field is only decoded if the reservation is of type Hard, or Soft.  
         [0070]     According to aspects of the present invention, when a receiver notices a reservation in its neighborhood (i.e., from a neighboring device) that is overlapping with its own reservation, the receiver informs its transmitter about the collision. This notification may be included in the performance of step  516 . In an embodiment, the receiving device points out the colliding MAS slots by leaving the indication of these slots from the DRP IE that it transmits. This provides an indication to the transmitter that those particular slots are not to be used for transmitting data to the receiver. In a further embodiment, the receiving device points out the colliding MAS slots as unavailable in a bit vector that it transmits in an AIE. However, in further embodiments of the present invention, the receiver points out the colliding slots by both leaving the colliding slots out of the DRP IE and sending an AIE that indicates the colliding slots as unavailable. This helps the transmitter identify any free MAS slots.  
       V. RECEIVER INITIATED NEGOTIATION  
       [0071]     A further alternative for performing step  516  involves the receiver-initiated exchange of messages between the receiver and the sender. Accordingly,  FIG. 6  is a diagram showing an interaction between a transmitting device  602  and a receiving device  604  that involves the exchange of such messages. These messages may be exchanged through beacon transmissions. Alternatively, these messages may be exchanged through allocated communications bandwidth (i.e., existing reservations). An advantage of this interaction is that it may save time (i.e., one superframe) over the aforementioned AIE approach, which involves the DRP reservation mechanism.  
         [0072]     The interaction of  FIG. 6  includes multiple steps. For instance, in a step  610 , receiving device  604  sends a ChangeRecommendation message to transmitting device  604 . As shown in  FIG. 6 , the ChangeRecommendation message includes a reservation recommendation parameter and an AIE. The reservation recommendation parameter indicates which MAS slots the receiver is recommending and the AIE shows all the possibilities.  
         [0073]     Transmitting device  602  receives and processes this message. Based on this, transmitting device  602  generates and sends a ChangeRequest message in a step  612 . As shown in  FIG. 6 , this message includes the newly requested reservations (allocations) as well as the current ones.  
         [0074]     Upon receipt of the ChangeRequest message, the receiving device determines whether to accept this request. If accepted, receiving device  604  sends a ChangeResponse message to transmitting device  602  in a step  614 .  
       VI. DEVICE IMPLEMENTATION  
       [0075]      FIG. 7  is a diagram of a wireless communications device  700 , which may operate according to the techniques of the present invention. This device may be used in various communications environments, such as the environment of  FIG. 1 . As shown in  FIG. 7 , device  700  includes a physical layer (PHY) controller  702 , a media access controller (MAC)  703 , an OFDM transceiver  704 , upper protocol layer(s)  705 , and an antenna  710 .  
         [0076]     MAC controller  703  generates frames (data transmissions) and beacons for wireless transmission. In addition, MAC controller  703  receives and processes frames and beacon transmissions that are originated from remote devices. MAC controller  703  exchanges these frames and beacon transmissions with PHY controller  702 . In turn, PHY controller  702  exchanges frames and beacon transmissions with OFDM transceiver  704 . Further, MAC controller  703  identifies interfering conditions and initiates the removal of such conditions. For example, in embodiments, MAC controller  703  may perform steps of  FIG. 5 .  
         [0077]      FIG. 7  shows that OFDM transceiver  704  includes a receiver portion  750  and a transmitter portion  760 . Transmitter portion  760  includes an inverse fast fourier transform (IFFT) module  714 , a zero padding module  716 , an upconverter  718 , and a transmit amplifier  720 . IFFT module  714  receives frames for transmission from PHY controller  702 . For each of these frames, IFFT module  714  generates an OFDM modulated signal. This generation involves performing one or more inverse fast fourier transform operations. As a result, this OFDM modulated signal includes one or more OFDM symbols. This signal is sent to zero padding module  716 , which appends one or more “zero samples” to the beginning of each OFDM symbol to produce a padded modulated signal. Upconverter  718  receives this padded signal and employs carrier-based techniques to place it into one or more frequency bands. These one or more frequency bands are determined according to a frequency hopping pattern, such as one or more of the TFCs. As a result, upconverter  718  produces a frequency hopping signal, which is amplified by transmit amplifier  720  and transmitted through antenna  710 .  
         [0078]      FIG. 7  shows that receiver portion  750  includes a downconverter  722 , a receive amplifier  724 , and a fast fourier transform (FFT) module  726 . These components (also referred to as a receiver) are employed in the reception of wireless signals from remote devices. In particular, antenna  710  receives wireless signals from remote devices that may employ frequency hopping patterns, such as one or more of the TFCs. These signals are sent to amplifier  724 , which generates amplified signals. Amplifier  724  sends the amplified signals to downconverter  722 . Upon receipt, downconverter  722  employs carrier-based techniques to convert these signals from its one or more frequency hopping bands (e.g., TFC bands) into a predetermined lower frequency range. This results in modulated signals, which are received by FFT module  726 , which performs OFDM demodulation on these signals. This demodulation involves performing a fast fourier transform for each symbol that is conveyed in the amplified signals.  
         [0079]     As a result of this demodulation, FFT module  726  produces one or more frames, which are sent to PHY controller  702 . These frames may convey information, such as payload data and protocol header(s). Upon receipt, PHY controller  702  processes these frames. This may involve removing certain PHY layer header fields, and passing the remaining portions of the frames to MAC controller  703 .  
         [0080]     As shown in  FIG. 7 , device  700  further includes one or more upper protocol layers  705 . These layers may involve, for example, user applications. Accordingly, upper layers  705  may exchange information with remote devices. This involves layer(s)  705  exchanging protocol data units with MAC controller  703 . In turn, MAC controller  703  operates with PHY controller  702  and transceiver  704  to transmit and receive corresponding wireless signals.  
         [0081]     The devices of  FIG. 7  may be implemented in hardware, software, firmware, or any combination thereof. For instance, upconverter  718 , transmit amplifier  720 , receive amplifier  724 , and downconverter  722  may include electronics, such as amplifiers, mixers, and filters. Moreover, implementations of device  700  may include digital signal processor(s) (DSPs) to implement various modules, such as scanning module  706 , IFFT module  714 , zero padding module  716 , and FFT module  726 . Moreover, in embodiments of the present invention, processor(s), such as microprocessors, executing instructions (i.e., software) that are stored in memory (not shown) may be used to control the operation of various components in device  700 . For instance, components, such as PHY controller  702  and MAC controller  703 , may be primarily implemented through software operating on one or more processors.  
         [0082]     One such implementation of the  FIG. 7  architecture is shown in  FIG. 8 . This diagram illustrates the terminal device implemented according to one embodiment of the present invention. As shown in  FIG. 8 , this implementation includes a processor  810 , a memory  812 , and a user interface  814 . In addition, the implementation of  FIG. 8  includes OFDM transceiver  704  and antenna  710 . These components may be implemented as described above with reference to  FIG. 7 . However, the implementation of  FIG. 8  may be modified to include different transceivers that support other wireless technologies.  
         [0083]     Processor  810  controls device operation. As shown in  FIG. 8 , processor  810  is coupled to transceiver  704 . Processor  810  may be implemented with one or more microprocessors that are each capable of executing software instructions stored in memory  812 , for example, as a computer system.  
         [0084]     Memory  812  includes random access memory (RAM), read only memory (ROM), and/or flash memory, and stores information in the form of data and software components (also referred to herein as modules). These software components include instructions that can be executed by processor  810 . Various types of software components may be stored in memory  812 . For instance, memory  812  may store software components that control the operation of transceiver  704 . Also, memory  812  may store software components that provide for the functionality of PHY controller  702 , MAC controller  703 , and upper protocol layer(s)  705 .  
         [0085]     In addition, memory  812  may store software components that control the exchange of information through user interface  814 . As shown in  FIG. 8 , user interface  814  is also coupled to processor  810 . User interface  814  facilitates the exchange of information with a user.  FIG. 8  shows that user interface  814  includes a user input portion  816  and a user output portion  818 .  
         [0086]     User input portion  816  may include one or more devices that allow a user to input information. Examples of such devices include keypads, touch screens, and microphones. User output portion  818  allows a user to receive information from the device. Thus, user output portion  818  may include various devices, such as a display, and one or more audio speakers (e.g., stereo speakers) and a audio processor and/or amplifier to drive the speakers. Exemplary displays include color liquid crystal displays (LCDs), and color video displays.  
         [0087]     The elements shown in  FIG. 8  may be coupled according to various techniques. One such technique involves coupling transceiver  704 , processor  810 , memory  812 , and user interface  814  through one or more bus interfaces. In addition, each of these components is coupled to a power source, such as a removable and/or rechargeable battery pack (not shown).  
       VII. CONCLUSION  
       [0088]     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not in limitation. For instance, although examples have been described involving MBOA communications, other short-range and longer-range communications technologies are within the scope of the present invention. Moreover, the techniques of the present invention may be used with signal transmission techniques other than OFDM.  
         [0089]     Accordingly, it will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.