Extendable Frequency Hopping Timeslots in Wireless Networks

• US 20120155284A1
• Filed: 12/17/2010
• Published: 06/21/2012
• Est. Priority Date: 12/17/2010
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Shaffer, Shmuel, Shetty, Sandeep Jay, Vasseur, Jean-Philippe
• Granted Patent: US 8,842,630 B2
• Time in Patent Office: Days
• US Class Current: 370/242
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

In one embodiment, a wireless transmitting node in a frequency hopping wireless network may determine whether a packet can be transmitted within a particular timeslot of a frequency hopping sequence based on a length of the packet. If unable to transmit the packet within the particular timeslot, the transmitting node extends the particular timeslot into a subsequent timeslot to allow transmission of the packet within the extended timeslot at a frequency associated with the particular timeslot. Once the extended timeslot ends, the transmitting node and receiving node hop frequencies into the subsequent timeslot to synchronize with the rest of the network that already hopped at the conventional rate. In another embodiment, a wireless receiving node may also extend the particular timeslot into a subsequent timeslot to allow reception of a packet that would extend beyond the particular timeslot, and may hop frequencies upon expiration of the extended timeslot.

Claims

1. A method, comprising:

determining, based on a length of a packet to transmit from a wireless node in a frequency hopping wireless network, whether transmission of the packet can be completed within a particular timeslot of a frequency hopping sequence; and

in response to determining that the packet transmission cannot be completed within the particular timeslot;

extending the particular timeslot into at least one subsequent timeslot sufficient to allow transmission of the packet to be completed within a combination of the particular timeslot and the extended timeslot;

transmitting at least some of the packet in the extended timeslot at a first frequency associated with the particular timeslot; and

changing from the first frequency to one or more second frequencies at some point after expiration of the extended timeslot.

2. The method as in claim 1, wherein extending the particular timeslot comprises:

defining the extended timeslot to include time to receive an acknowledgement (ACK) from an intended receiver of the packet before expiration of the extended timeslot.

3. The method as in claim 1, further comprising:

randomizing a start of packet transmission within the particular timeslot,

wherein determining whether the packet can be transmitted within the particular timeslot is based on the randomized start.

4. The method as in claim 3, wherein the randomized start is one of a plurality of sub-timeslots within the particular timeslot.

5. The method as in claim 1, further comprising:

determining whether an intended receiver supports the extended timeslot; and

in response to determining that support exists at the intended receiver for the extended timeslot, extending the particular timeslot.

6. The method as in claim 1, further comprising:

selecting a parent in a directed acyclic graph (DAG) based on whether the parent supports extended timeslots.

7. An apparatus, comprising:

one or more wireless network interfaces configured to communicate in a frequency hopping wireless network;

a processor coupled to the wireless network interfaces and adapted to execute one or more processes; and

a media access control (MAC) module coupled to the processor and the wireless network interfaces, the MAC module configured to;

determine, based on a length of a packet to transmit from a wireless node in a frequency hopping wireless network, whether transmission of the packet can be completed within a particular timeslot of a frequency hopping sequence; and

in response to determining that the packet transmission cannot be completed within the particular timeslot;

extend the particular timeslot into at least one subsequent timeslot sufficient to allow transmission of the packet to be completed within a combination of the particular timeslot and the extended timeslot;

transmit at least some of the packet in the extended timeslot at a first frequency associated with the particular timeslot; and

change from the first frequency to one or more second frequencies at some point after expiration of the extended timeslot.

8. The apparatus as in claim 7, wherein the MAC module is further configured to define the extended timeslot to include time to receive an acknowledgement (ACK) from an intended receiver of the packet before expiration of the extended timeslot.

9. The apparatus as in claim 7, wherein the MAC module is further configured to:

randomize a start of packet transmission within the particular timeslot, wherein the determination of whether the packet can be transmitted within the particular timeslot is based on the randomized start.

10. The apparatus as in claim 9, wherein the randomized start is one of a plurality of sub-timeslots within the particular timeslot.

11. The apparatus as in claim 7, wherein the MAC module is further configured to:

determine whether an intended receiver supports the extended timeslot; and

in response to determining that support exists at the intended receiver for the extended timeslot, extend the particular timeslot.

12. The apparatus as in claim 7, wherein the MAC module is further configured to:

select a parent in a directed acyclic graph (DAG) based on whether the parent supports extended timeslots.

19. The apparatus as in claim 7, wherein the MAC module is further configured to:

perform an error check on the header of the packet prior to determining whether the destination address corresponds to the wireless node.

20. The apparatus as in claim 7, further comprising:

a memory configured to store a process, the process when executed operable to;

receive a request from a child node in a directed acyclic graph (DAG) to determine whether the apparatus as a parent node supports extended timeslots; and

respond to the child node that the apparatus does support extended timeslots.

13. A method, comprising:

receiving a header of a wireless packet at a wireless node in a frequency hopping wireless network, the header indicating a destination address and a length of the packet;

in response to the destination address not corresponding to the wireless node, ignoring a remainder of the packet; and

in response to the destination address corresponding to the wireless node;

determining whether receipt of the packet can be completed within a particular timeslot of a frequency hopping sequence; and

in response to determining that receipt of the packet cannot be completed within the particular timeslot;

extending the particular timeslot into at least one subsequent timeslot sufficient to allow receipt of the packet to be completed within a combination of the particular timeslot and the extended timeslot;

receiving at least some of the packet in the extended timeslot at a first frequency associated with the particular timeslot; and

changing from the first frequency to one or more second frequencies at some point after expiration of the extended timeslot.

14. The method as in claim 13, further comprising:

defining the extended timeslot to include time to transmit an acknowledgement (ACK) before expiration of the extended timeslot; and

transmitting the ACK to an originator of the packet within the extended timeslot at the frequency associated with the particular timeslot in response to receiving the remainder of the packet.

15. The method as in claim 13, further comprising:

performing an error check on the header of the packet prior to determining whether the destination address corresponds to the wireless node.

16. The method as in claim 13, further comprising:

receiving, by the wireless node acting as a parent node in a directed acyclic graph (DAG), a request from a child node to determine whether the parent node supports extended timeslots; and

responding to the child node that the parent node does support extended timeslots.

17. An apparatus, comprising:

one or more wireless network interfaces configured to receive a header of a wireless packet in a frequency hopping wireless network, the header indicating a destination address and a length of the packet;

a processor coupled to the wireless network interfaces and adapted to execute one or more processes; and

a media access control (MAC) module coupled to the processor and the wireless network interfaces, the MAC module configured to;

ignore a remainder of the packet in response to the destination address not corresponding to the wireless node; and

in response to the destination address corresponding to the wireless node;

determining whether receipt of the packet can be completed within a particular timeslot of a frequency hopping sequence; and

in response to determining that receipt of the packet cannot be completed within the particular timeslot;

extending the particular timeslot into at least one subsequent timeslot sufficient to allow receipt of the packet to be completed within a combination of the particular timeslot and the extended timeslot;

receiving at least some of the packet in the extended timeslot at a first frequency associated with the particular timeslot; and

changing from the first frequency to one or more second frequencies at some point after expiration of the extended timeslot.

18. The apparatus as in claim 17, wherein the MAC module is further configured to:

defining the extended timeslot to include time to receive an acknowledgement (ACK) from an intended receiver of the packet before expiration of the extended timeslot; and

transmit the ACK to an originator of the packet within the extended timeslot at the frequency associated with the particular timeslot in response to receiving the remainder of the packet.