EFFICIENT ALLOCATION OF SHARED BANDWIDTH

Abstract

The present invention, generally speaking, provides for sharing of bandwidth of a shared medium between multiple devices. In one embodiment, the shared medium is structured in accordance with a frame or superframe structure, each frame or superframe having medium access slots of specified time duration defined therein, groups of N contiguous medium access slots defining different allocations zones, groups of M medium access slots defining coordinated sets of medium access slots, wherein the medium access slots of a coordinated set belonging to different allocation zones are equally spaced in time. A device identifies a reservation as regular or irregular, wherein a regular reservation causes the entire medium access slots in one or more coordinated sets to be allocated. In the case of either a regular or an irregular reservation, allocating medium access slots such that a number of unallocated contiguous medium access slots within each allocation zone is maximized. The contiguous unallocated medium access slots separate the group of regular allocations and the group of irregular allocations within each allocation zone.

Description

The present invention relates to bandwidth sharing by communication devices.

In communication networks, devices are often required to share bandwidth of a shared medium, wired or wireless. One example of such a network is a wireless PAN (personal area network). Such networks are ad hoc, meaning that devices may join the network or leave the network frequently without advance warning. A mechanism is then required to coordinate sharing of the medium—in this instance wireless spectrum. The same problem occurs to various degrees in various different types of networks.

A particular challenge arises in balancing device access against efficient use of medium. In one proposed solution, a device is free to reserve resource with relatively few restrictions. Efficiency of medium use therefore suffers.

The present invention, generally speaking, provides for sharing of bandwidth of a shared medium between multiple devices. In one embodiment, the shared medium is structured in accordance with a frame or superframe structure, each frame or superframe having medium access slots of specified time duration defined therein, groups of N contiguous medium access slots defining different allocations zones, groups of M medium access slots defining coordinated sets of medium access slots, wherein the medium access slots of a coordinated set belonging to different allocation zones are equally spaced in time. A device identifies a reservation as regular or irregular, wherein a regular reservation causes the entire medium access slots in one or more coordinated sets to be allocated. In the case of a regular or an irregular reservation, allocating medium access slots such that a number of unallocated contiguous coordinated sets of medium access slots within each allocation zone is maximized.

The present invention may be more fully understood from the following description in conjunction with the appended drawing. In the drawing:

FIG. 1 is a block diagram of a system in which the present invention may be used.

FIG. 2 is a diagram illustrating a superframe structure.

FIG. 3 is a diagram of the superframe structure of FIG. 2, illustrating allocation zones.

FIG. 4 is a diagram of the superframe structure of FIG. 2, illustrating coordinated MAS sets.

FIG. 5 is a diagram illustrating conventional allocation within the superframe.

FIG. 6 is a diagram illustrating allocation within the superframe in accordance with one aspect of the present invention.

FIG. 7 is a diagram illustrating allocation within the superframe in accordance with one aspect of the present invention.

FIG. 8 is a diagram illustrating an allocation example in accordance with the present invention.

Referring now to FIG. 1, a block diagram is shown of an exemplary system in which the present invention may be used. A number of devices, in this case wireless PAN devices, share a medium, in this case wireless spectrum. Further details of a device are shown. The device includes a hardware subsystem and a software subsystem. A medium access controller (MAC) controls access of the device to the shared medium. In the case of a wireless PAN device, the MAC may be of a type specified in the standard IEEE 802.15.3, for example. Typically, the MAC will be realized in a combination of hardware and software.

The shared medium may be organized in accordance with a known superframe structure illustrated in FIG. 2. The number of time slots (also referred to as Medium Access Slots, or MAS) in a superframe is 256. For conceptual and illustrative purposes, the timeslots are arranged in columns of 16 as shown in FIG. 2. Typically, a column is referred to as an allocation zone. One column, however, is set aside as a beacon zone. In the case of 256 MAS and columns of 16 MAS, there is one beacon zone (the first column) and 15 allocation zones as shown in FIG. 3. A row is referred to as a coordinated MAS set. In the present example, there are 16 coordinated MAS sets, numbered 0-15, as shown in FIG. 4.

A conventional Distributed Reservation Protocol (DRP) may be used by devices to gain access to the shared medium. In DRP, an aspiring reservation owner listens to the beacons and find unallocated MAS identified in the beacons. It then announces in its own beacon its intention to use some of the unallocated MAS, which constitutes a reservation.

All other devices are obliged to honor the reservations identified in the beacons. [A DEVICE OBTAINS A BEACON by receiving beacon frames during each beacon period.]

Conventional methods of allocation suffer the problem that unallocated MAS are often scattered. An example of such an allocation is shown in FIG. 5. Allocation and use of scattered MAS is burdensome and inefficient and is likely to adversely impact device operation.

A more efficient allocation may be achieved by performing allocation in accordance with one, more preferably both, of the following rules:

1. A MAS allocation in each allocation zone shall be made so as to leave the contiguous unallocated MAS in the zone as large as possible, by taking advantage of the requirements of different application types, which afford some flexibility in the location of each MAS allocation.

2. A set of regular MAS (i.e., a multiple of 15) shall be allocated in one end of the allocation map and an irregular MAS allocation (i.e., all others) in the other end (as shown below), which minimizes the chance of unallocated MAS being trapped by allocated MAS.

Application of the first rule is illustrated in FIG. 6. Without application of the rule, unallocated MAS within an allocation zone become scattered. With application of the rule, unallocated MAS within an allocation zone are contiguous.

Application of the second rule is illustrated in FIG. 7. Allocations are divided into two different groups, Group I and Group II. Group I includes allocations of one or more complete coordinated MAS sets. In the illustrated example, Group I allocations are made from the bottom of the superframe upward. Group II includes all other allocations. In the illustrated example, Group II allocations are made from the top of the superframe downward. Unallocated MAS are located in the middle region of the superframe.

Applied together to the example of FIG. 5, the foregoing rules result in the allocation of FIG. 8. Comparing the two allocations, the same number of MAS are allocated to each device. However, in FIG. 8, unallocated MAS are contiguous in each zone. This arrangement maximizes the efficiency of contention-based channel access.

It will be appreciated by those or ordinary skill in the art that the invention can be embodied in other specific forms without departing from the spirit or essential character thereof. The disclosed embodiments are therefore intended in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description, and all changes which fall within the meaning and range of equivalents thereof are intended to be embraced therein.

Claims

1. A method of sharing bandwidth of a shared medium between multiple devices, the shared medium being structured in accordance with a frame or superframe structure, each frame or superframe having medium access slots of specified time duration defined therein, groups of N contiguous medium access slots defining different allocations zones, groups of M medium access slots defining coordinated sets of medium access slots, wherein the medium access slots of a coordinated set belonging to different allocation zones are equally spaced in time, the method comprising a device performing the steps of: identifying a reservation as regular or irregular, wherein a regular reservation causes the entire medium access slots in one or more coordinated sets to be allocated; and in the case of either a regular or an irregular reservation, allocating medium access slots such that a number of unallocated contiguous coordinated sets of medium access slots within each allocation zone is maximized.

2. A method of sharing bandwidth of a shared medium between multiple devices, the shared medium being structured in accordance with a frame or superframe structure, each frame or superframe having medium access slots of specified time duration defined therein, groups of N contiguous medium access slots defining different allocations zones, groups of M medium access slots defining coordinated sets of medium access slots, wherein the medium access slots of a coordinated set belonging to different allocation zones are equally spaced in time, the method comprising a device performing the steps of: identifying a reservation as regular or irregular, wherein a regular reservation causes the entire medium access slots in one or more coordinated sets to be allocated; and preferring a first coordinated set of medium access slots and coordinated sets of medium access slots contiguous thereto for allocations corresponding to regular reservations; and preferring part of a second coordinated set of medium access slots and coordinated sets of medium access slots contiguous thereto for allocations corresponding to irregular reservations; wherein the first coordinated set of medium access slots and the second coordinated set of medium access slots are as widely separated as possible within the two-dimensional representation of the frame or superframe structure as shown in FIG. 7.

3. A device that accesses a shared medium, the shared medium being structured in accordance with a frame or superframe structure, each frame or superframe having medium access slots of specified time duration defined therein, groups of N contiguous medium access slots defining different allocations zones, groups of M medium access slots defining coordinated sets of medium access slots, wherein the medium access slots of a coordinated set belonging to different allocation zones are equally spaced in time, the device comprising: means for identifying a reservation as regular or irregular, wherein a regular reservation causes the entire medium access slots in one or more coordinated sets to be allocated; and means for, in the case of either a regular or an irregular reservation, allocating medium access slots such that a number of unallocated contiguous medium access slots within each allocation zone is maximized.

4. A device that accesses a shared medium, the shared medium being structured in accordance with a frame or superframe structure, each frame or superframe having medium access slots of specified time duration defined therein, groups of N contiguous medium access slots defining different allocations zones, groups of M medium access slots defining coordinated sets of medium access slots, wherein the medium access slots of a coordinated set belonging to different allocation zones are equally spaced in time, the device comprising: means for identifying a reservation as regular or irregular, a regular reservation causes the entire medium access slots in one or more coordinated sets to be allocated; and means for preferring a first coordinated set of medium access slots and coordinated sets of medium access slots contiguous thereto for allocations corresponding to regular reservations; and means for preferring part of a second coordinated set of medium access slots and coordinated sets of medium access slots contiguous thereto for allocations corresponding to irregular reservations; wherein the first coordinated set of medium access slots and the second coordinated set of medium access slots are as widely separated as possible within the two-dimensional representation of the frame or superframe structure as shown in FIG. 7.