GB2307624A - Data transmission for channel hopping communication - Google Patents
Data transmission for channel hopping communication Download PDFInfo
- Publication number
- GB2307624A GB2307624A GB9523970A GB9523970A GB2307624A GB 2307624 A GB2307624 A GB 2307624A GB 9523970 A GB9523970 A GB 9523970A GB 9523970 A GB9523970 A GB 9523970A GB 2307624 A GB2307624 A GB 2307624A
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- Prior art keywords
- frame
- data
- communication
- slot
- transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/713—Spread spectrum techniques using frequency hopping
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/713—Spread spectrum techniques using frequency hopping
- H04B1/7156—Arrangements for sequence synchronisation
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
A communication link is established in a system (100) having a channel hopping protocol for operating on a set of communication channels. The channel hopping protocol provides for communication slots on successive communication channels, each communication slot having a slot duration corresponding to a time requirement for channel hopping. The data is packaged into frames, such that each frame has a transmission time less than the slot duration. Data is transferred across the communication link such that transmission of any particular frame, does not span across multiple communication slots.
Description
DATA TRANSMISSION METHOD FOR A CHANNEL HOPPING COMMUNICATION SYSTEM This invention relates in general to radio communication systems, and in particular, to data transmission over radio communication systems employing a channels hopping protocol.
Backgund of i Invention
There are a growing number of applications which incorporate radio frequency (RF) communication devices to transfer data over a wireless communication link. Examples include data collection and presentation applications using portable terminals, personal communicatioq devices, monitor and control devices, and the like.
Generally, these RF devices communicate over portions of the RF band made available by a regulatory body under license for such purposes. A limited portion of the RF band has also been made available for unlicensed use, provided that certain limitations on their use are observed. Under one such limitation, a spread spectrum technique is required for transmission in the frequency band. Available spread spectrum techniques include direct sequencing, and frequency hopping. Direct sequencing techniques generally require the use of wide band RF devices and complicated circuitry for transmitting and recovering signals. These factors contribute to the expense and complexity of a device that implements direct sequencing.
For transmissions using a frequency hopping technique, the available frequency band is divided into a number of frequency channels, and limitations are imposed on the maixmum duration of continuos use of a particular frequency channel, and on the minimum time between reuse of the same frequency channel. In a typical frequency hopping protocol, the set of frequency channels available is organised into a sequence, and communication occurs in turn on each channel of the sequence after a prescribed time interval, commonly referred to as a channel hop time or dwell time. Thus, in a frequency hopping system regular switching among frequency channels occurs at prescribed intervals.
Many communication devices that implement frequency hopping include dedicated circuitry that controls the switching among the frequency channels of the sequence. Such switching circuitry is usually available from various manufacturers as a self-contained module. The switching between frequency channels can require an appreciable amount of time. In order to facilitate communication across a communication link while the frequency channel switching is occurring, a typical frequency hopping protocol module employs buffering and other control mechanism to ensure that information communicated during switching is ultimately transmitted when the switching has completed. The buffering and handshaking required for synchronisation of transmissions add significantly to the cost of such frequency hopping protocol implementing modules.However, for satisfying a spread spectrum transmission requirement, a frequency hopping approach tends to be less expensive than a direct sequencing approach.
Generally, a communication device also includes logic implementing a communication protocol for exchanging information, such as voice or data, over a communication link established over the set of frequency channels. In prior art designs, the communication protocol is independent of the frequency hopping implementation, and as such, the frequency hopping protocol is transparent to the communication protocol.
Thus, the transmission and receipt of information over a communication link occurs independently of the underlying switching of frequency channels according to the frequency hopping protocol.
There has been a continuous effort to deliver lower cost data communications systems, particularly, for use on available unlicensed frequency bands. A frequency hopping protocol implementation offers opportunities for cost savings when implementing spread spectrum techniques. However, available frequency hopping protocol implementation modules tend to incorporate expensive circuitry for synchronisation and other handshaking requirements to facilitate communication during frequency switching. Accordingly, a need exists for new approach in handling transmissions over a communication link established using a frequency hopping protocol.
Summary of the Invention
The present invention provides for a method of transferring data over communication link established under a channels hopping protocol.
The channel hopping protocol provides for communication slots on successive communication channels, each communication slot having a slot duration corresponding to a time requirement for channel hopping.
According to the present invention, data for transmission is packaged into one or more frames for transmission, each transmission frame having a transmission time less that the slot duration. The transferring of data across the communication link is regulated so that the transmission of any particular frame does not span across multiple communication slots.
Brief Description of the Drawing FIG. 1 is a block diagram of a data collection system employing wireless communication links, in accordance with the present invention.
FIG. 2 is a timing diagram showing the progression of a communication slot established on a set of three frequency channels, in accordance with the present invention.
FIG. 3 is a block representation of selected frame types, in accordance with the present invention.
FIG. 4 is a table of sample transactions, in accordance with the present invention.
FIG. 5 is a timing diagram highlighting communication slot control by a master device, in accordance with the present invention.
FIG. 6 is a timing diagram of communication between a master device and a remote device, in accordance with the present invention.
FIG. 7 is a flowchart of procedures for transferring data over a wireless communication link employing a channel hopping protocol, in accordance with the present invention.
FIG. 8 is a flowchart of procedures of data transactions between transceivers, in accordance with the present invention.
Detailed Description of the Preferred Embodiment
While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward.
Referring to FIG. 1, a data collection system 100 is shown, in accordance with the present invention. In the preferred embodiment, the system 100 comprises a central or master unit 105, and remote or peripheral units 110, 120, 130, which interface with the master unit 105 via wireless communication links. According to the present invention, the master unit 105 and remote units 110, 120, 130 comprise radio transceivers that operate under a channel or frequency hopping protocol on portions of the radio frequency band. Preferably, the portions of radio frequency band are organised into a sequence communication channels. For example, a communication channel may comprise one or more frequency channels, such as a transmit and receive pair, or similar grouping.The channel hopping protocol defines, as a parameter, a channel hop time or maximum dwell time, i.e., a period of time which a transceiver, or group of transceivers, may spend continuously utilising a given communication channel. The channel hopping protocol may also include other parameters, such as the minimum time that must elapse, after a maximum dwell time has expired, between reuse of the same channel.
In a typical channel hopping protocol environment, available communication channels are organised into a sequence and a protocol is provided for accessing this sequence of communication channels. Once access is obtained, a time slot having a maximum duration, equivalent to the time requirement for channel hopping, will be available on successive channels of the sequence. A communication slot, as used herein, refers to a particular time slot on a particular communication channel. The communication slot has a slot duration corresponding to a time requirement for channels hopping, and would ordinarily be equivalent to the maximum dwell time.
FIG. 2 is a timing diagram 200 showing the progression of a communication slot established on a set of three frequency channels, in accordance with the present invention. At time T1, a communication slot exists on frequency F1. This communication slot has a slot duration of TH.
At time T2, another communication slot appears at frequency F2.
Similarly, at T3, a communication slot is at frequency F3. At time T4, a communication slot is at frequency F1, and at time Tg, at frequency F2, and so on. For a given communication link, the frequency hopping protocol governs the use of a particular communication channel at a particular time.
Once a communication link has been established, the exchange of information between trasnceivers is ordinarily governed by a data communication protocol. Data as used herein refers to any kind of information, including voice, video, and the like. For data transfers between transceivers, the data communication protocol may govern data formats, permissible transactions between transceivers, handshaking, and the like. According to the present invention, a data communication protocol is provided that is dependent on one or more channel hopping protocol parameters. This represents a significant departure from prior art approaches in which the data communication protocol is independent of the channel hopping protocol parameters.In the data communication protocol of the present invention, communication betwen transceivers is governed or regulated such that there are no transmissions that span across multiple communication slots. Thus, a transmission must be initiated and completed within a single communciation slot. Under the communication protocol, data transmissions occur using one of a predefined set of frame types as part of a transaction.
FIG. 3 is a block representation of selected frame types of the preferred embodiment. A request frame type 310 includes an identification and control information section 311, a data section 312, and an error detection information section 313. An acknowledge frame type 320 includes an identification and control information section 321, and an error detection information section 323. A poll frame type 330 includes an identification and control information section 331, and an error detection information section 333. A data frame type 340 includes an identification and control information section 341, a data section 342, and an error detection information section 343. The identification and control information sections include length of the particular frame, sequence identification information, source and destination information, and the like.The error detection information is preferably an error code generated for the frame, such as a cyclic redundancy code. According to the data communication protcol, communication between transceivers occurs using information packaged into one or more frame types. Data transfers between transceivers are governed by transactions which ordinarily include an exchange of frames between the transceivers. In the preferred embodiment, transactions for data transmissions include at least one frame from the master unit and at least one from a remote unit.
FIG. 4 is a table of sample transactions 400, in accordance with the present invention. Each sample transaction involves the exchange of at least one frame of information between two transceivers. In a first transaction 410, a poll frame is transmitted by the master unit, and a data frame is transmitted in response by the remote unit. In a second transaction 420, a poll frame is transmitted by the master unit, and an acknowledge frame is transmitted in response by the remote unit. In a third transaction 430, an idle frame is transmitted by the master unit that indicates that a communication slot is available for use. In the preferred embodiment, an idle frame is a special form of the acknowledge frame type described above. A request frame is transmitted in response by the remote unit, and the master unit acknowledges this request frame.In a fourth transaction 440, a data frame is transmitted by the master, and an acknowledge frame is transmitted in response by a remote unit.
In the preferred embodiment, the data communication protocol also allows the master unit to exercise control over access to any communication slot. The master transmits, at the start of each communication slot, information that governs the use of the remaining portion of the communication slot. FIG. 5 is a timing diagram 500 highlighting master unit control of the communication slot, in accordance with the present invention. At the beginning of each communication slot, the master unit transmits either a request for information, an acknowledgement of information transmitted by a remote, or an indication that the remainder of the communication slot is available for remote initiated transactions.
In the communication slot corresponding to frequency F1, the master transmits a poll frame 501, which indicates that a remote unit is being polled for data. During the same time slot on frequency F1, a remote unit responds with a data frame 511. At the communication slot corresponding to frequency F2, the master transmits an acknowledge frame 502 to the previous data frame sent by the remote unit plus a new poll to the same unit. The remote transmits a final data frame 512 larked as final the identification and control part of the frame2. At the communication slots corresponding to frequency F3 the master responds (503) with an acknowledgement to the previous frame plus an 'idle' indication to signal that the rest of the slot is available for remote initiated transactions.At the communication slots corresponding to frequency, F4, the master transmits an idle frame, 504, to indicate that this communication slot is available for remote initiated transactions. At the communication slot corresponding to frequency F4, a second remote transmits a request frame 524, which is acknowledged at frequency Fs by an acknowledge frame 505 from the master.
FIG. 6 is a timing diagram 600 of communication between a master device and a remote device, in accordance with the present invention.
FIG. 7 is a flowchart of procedures used by a transceiver for data transmission, in accordance with the present invention. Referring to
FIGs. 6 and 7, a data transfer session between master and a remote unit is described, assuming that a communication link has already been established that uses frequency hopping. The master transmits an idle frame 601 in a communication slot corresponding to frequency F1. The remote unit transmits a request frame 611. The master then obtains data for transmission, step 710. With its first data frame, the Master will also acknowledge the previous request from the remote.
The data is packaged into one or more data frames, step 720. Each data frame is formed by combining at least a portion of the data with identification information and error detection information calculated for the frame. As communication is restricted such that transmission for any frame across the communication link is initiated and completed within a single communication slot, the data is packaged such that each frame has a transmission time less than the slot duration of the communication slot.
Preferably, each data frame is restricted to a size that can be transmitted and acknowledged within the slot duration.
One or more transactions are formed to transfer all the data, step 730. Each transaction including at least one transmitted frame and at least one received frame. For example, a data transfer transaction typically includes a data frame and an acknowledge frame. The data is then transferred across the communication link, using data transfer transactions, such that the transmission of any single frame does not span across multiple communication slots, step 740.
In one embodiment, each transaction is initiated and completed within a single communication slot. Thus, a transaction is selected for execution when operating within a particular communication slot. When the transaction can be completed within time remaining in the particular communication slot, the transaction is executed. When the transaction cannot be completed during time remaining in the communication slot, the execution of the transaction is delayed until operating within a communication slot on a subsequent communication channel of the successive communication channels.
Referring back to FIG. 6, data. together with an acknowledgement to the previous remote request in frame 611 is transmitted in data frame 603 and an acknowledge frame to this data from the Master 613 transmitted within the same communication slot. Similarly, data is transmitted in data frame 604 and acknowledged by acknowledge frame 614. Once the data transfer is completed, the master transmits idle frames 605, 606 in successive communication slots. A second remote, upon detecting the idle frame 606 begins a similar set of transactions starting with a request frame 626.
FIG. 8 is a flowchart of procedures summarizing data transfer transactions between transceivers, in accordance with the present invention. At the first transceiver, a first frame containing information is transmitted in a single time slot, step 810. In the case of a transceiver functioning as a master unit, a transmitted frame may represent a request for data transfer, an acknowledgement of a previously received frame, or an indication that a particular time slot is available for initiating unsolicited communications or a combination of the above. At a second transceiver, the transmitted frame is received, and data prepared in response, steps 820, 830. The data is packaged into multiple data frames such that each has a transmission time less than a single time slot, when the data has transmission time greater than the duration of a time slot, step 840.The data frames are transferred to the first transceiver such that transmission of each data frame is initiated and completed within a single time slot, step 850. All transmissions are governed such that no frame is transmitted across multiple communication slots.
The present invention offers significant advantages over the prior art. Because the data communication protocol restricts transmissions that span across communications slots, the circuitry that implements the frequency hopping protocol need not have logic to account for transmission requests that occur while switching channels. Thus, there may not be a need for buffering, synchronization, or other functions commonly employed by prior art frequency hopping implementation circuitry to avoid interference with the data communication protocol. This results in a less complex, less expensive implementation for data transfer over a communication link employing a frequency hopping protocol.
While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not so limited.
Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.
What is claimed is:
Claims (14)
1. A method of transferring data over a communication link employing a channel hopping protocol for operating on a plurality of communication channels, the channel hopping protocol providing for communication slots on successive communication channels, each communication slot having a slot duration corresponding to a time requirement for channel hopping, comprising the steps of:
packaging the data into a plurality of frames each having a
transmission time less than the slot duration; and
transferring the data across the communication link such that
transmission of any particular frame of the plurality of frames,
does not span across multiple communication slots.
2. The method of claim 1, wherein the step of packaging the data comprising the step of forming a data frame from a portion of the data according to one of a plurality of frame types.
3. The method of claim 2, wherein the step of forming a data frame comprises the step of combining the portion of the data with identification information and error detection information.
4. The method of claim 2, wherein the step of forming a data frame comprises the step of selecting a frame type from a set of frame types including a request frame type, an acknowledge frame type, a data frame type, and a poll frame type.
5. The method of claim 2, wherein the step of forming a data frame comprises the step of restricting the data frame to a size that can be transmitted and acknowledged within the slot duration.
6. The method of claim 1, 2, 3, 4, or 5, wherein the step of transferring comprises the step of restricting communications such that transmission for any frame across the communication link is initiated and completed within a single communication slot.
7. The method of claim 6, wherein the step of transferring comprises the steps of:
transmitting a first frame within a particular communication slot; and
receiving a second frame within the particular communication slot.
8. The method of claim 7, wherein the step of receiving comprises the step of receiving a second frame that acknowledges receipt of the first frame.
9. The method of claim 6, wherein the step of transferring comprises the step of executing a transaction comprising at least one transmitted frame and at least one received frame for which transmission is initiated and completed within a single communication slot.
10. The method of claim 6, wherein the step of transferring comprises the steps of:
forming a plurality of transactions for transferring all the data,
each transaction including at least one transmitted frame and at
least one received frame; and
executing each of the plurality of transactions such each transaction
is initiated and completed within a single communication slot.
11. The method of claim 10, wherein the step of executing comprises the steps of:
selecting a transaction for execution when operating within a
particular communication slot, the transaction including at least
one transmission frame containing at least a portion of the data;
executing the transaction, when the transaction can be completed
within time remaining in the particular communication slot;
delaying execution of the transaction until operating within a
communication slot on a subsequent communication channel of
the successive communication channels, when the transaction
cannot be completed during time remaining in the particular
communication slot.
12. In a radio communication system, including transceivers that operate on a plurality of frequency channels according to a frequency hopping protocol, the frequency hopping protocol providing for a time slot on successive frequency channels, the time slot having a duration corresponding to a time requirement for frequency hopping, a method comprising the steps of:
at a first transceiver:
initiating and completing transmission of a first frame during
a single time slot;
at a second transceiver:
receiving the first frame;
preparing data in response to the first frame;
packaging the data into a plurality of data frames, each data
frame having a transmission time less than the duration of a
time slot, when the data has transmission time greater than
the duration of a time slot; and
transmitting the plurality of data frames, such that
transmission of each data frame is initiated and completed
within a single time slot.
13. The method of claim 12, wherein the step of packaging comprises the step of combining at least a portion of the data with identification information and error detection information.
14. The method of claim 12, or 13, wherein the step of initiating and completing transmission of a first frame, comprises the step of transmitting one of:
a request for data transfer;
an acknowledgment of a previously received frame transmitted by
the second transceiver; and
an indication that a time slot is available for initiating
communications not solicited by the first transceiver.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9523970A GB2307624B (en) | 1995-11-23 | 1995-11-23 | Data transmission method for a channel hopping communication system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9523970A GB2307624B (en) | 1995-11-23 | 1995-11-23 | Data transmission method for a channel hopping communication system |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9523970D0 GB9523970D0 (en) | 1996-01-24 |
| GB2307624A true GB2307624A (en) | 1997-05-28 |
| GB2307624B GB2307624B (en) | 2000-02-09 |
Family
ID=10784341
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9523970A Expired - Fee Related GB2307624B (en) | 1995-11-23 | 1995-11-23 | Data transmission method for a channel hopping communication system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2307624B (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0167442A2 (en) * | 1984-06-29 | 1986-01-08 | Fairchild Weston Systems Inc. | Secure communication system |
| US4630282A (en) * | 1984-05-18 | 1986-12-16 | Mcdonnell Douglas Corporation | Frequency-hopping digital data link |
| EP0650274A2 (en) * | 1993-10-22 | 1995-04-26 | International Business Machines Corporation | Radio communications systems with fault tolerant frequency hopping synchronization |
| US5425051A (en) * | 1992-11-09 | 1995-06-13 | Norand Corporation | Radio frequency communication network having adaptive parameters |
| GB2292501A (en) * | 1982-07-06 | 1996-02-21 | Secr Defence | Frequency hopping |
-
1995
- 1995-11-23 GB GB9523970A patent/GB2307624B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2292501A (en) * | 1982-07-06 | 1996-02-21 | Secr Defence | Frequency hopping |
| US4630282A (en) * | 1984-05-18 | 1986-12-16 | Mcdonnell Douglas Corporation | Frequency-hopping digital data link |
| EP0167442A2 (en) * | 1984-06-29 | 1986-01-08 | Fairchild Weston Systems Inc. | Secure communication system |
| US5425051A (en) * | 1992-11-09 | 1995-06-13 | Norand Corporation | Radio frequency communication network having adaptive parameters |
| EP0650274A2 (en) * | 1993-10-22 | 1995-04-26 | International Business Machines Corporation | Radio communications systems with fault tolerant frequency hopping synchronization |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2307624B (en) | 2000-02-09 |
| GB9523970D0 (en) | 1996-01-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20071123 |