EP1397876A2

EP1397876A2 - Method and system for hybrid tdm and ip packet transmission over an air interface

Info

Publication number: EP1397876A2
Application number: EP02742192A
Authority: EP
Inventors: Juan-Carlos Zuniga; Tjo San Jao
Original assignee: Harris Corp
Current assignee: Harris Corp
Priority date: 2001-06-19
Filing date: 2002-06-19
Publication date: 2004-03-17
Also published as: EP1397876A4; CA2450901A1; WO2002103919A2; WO2002103919A3; WO2002103919A9; AU2002315346A1

Abstract

A method and system for generating a transmission frame (200) suitable for the concurrent transmission of real-time digitized audio data (212, 214, 216) and non-real time digital data (242, 244, 246) is disclosed. The method for generating the hybrid transmission frame (200) comprises the steps of prioritizing data requests (310) representative of audio and data transmission, wherein audio data requests are assigned a high priority allocating each of the audio data requests to one of a fixed duration channel (212, 214, 216) within a first portion (210) of the frame (200) and allocating the data transmission requests to a remaining portion (240) of said frame.

Description

Method and System for Hybrid TDM and IP Packet Transmission over an Air Interface

Claim of Priority

[0001] This application claims the benefit, pursuant to 35 USC 120, of the earlier filing date of U.S. Provisional Application Serial Number 60/298,887, entitled "Hybrid TDM and IP Packet Transmission over an Air Interface," having a filing date of June 19, 2001, which is incorporated by reference herein.

Background Of The Invention [0002] The present invention is directed toward point-to-multipoint wireless communication systems in general, and to Time Division Multiple Access (TDMA) Broadband Wireless Access (BWA) in particular.

[0003] Figure 1 illustrates a block diagram of a BWA system 100 using conventional TDMA (Time Division Multiple Access) technology employing a Frequency Division Duplex (FDD) duplexing scheme. The system consists of a plurality of Base Stations (BS) 110 in communication over network 115 and each BS 110 controlling and receiving information items from a plurality of associated Remote Stations (RS) 120 over corresponding networks 116, 117, 118. Base Station 110 continuously transmits signals, referred to as downstream transmission, through an omnidirectional antenna, or at least one sectional antenna, to each associated RS 120 assigned to a frequency carrier in Time Division Multiplex (TDM) mode. [0004] Each remote station 120 responds to the associated base station 110 downstream command or instruction, in turn. Transmission from remote station 120 to base station, referred to as an upstream transmission, on the other hand, is typically in a burst using a frequency carrier different than that of the downstream carrier frequency. As each RS 120, in the illustrated system shares the upstream carrier frequency, base station 1 10 sequentially commands each remote station, to transmit to avoid the collision of more than one remote station transmitting.

[0005] Base station 110, thus, includes a scheduling means, referred to as a scheduler, that decides when the next set of transmissions from a designated remote station 120 will occur. For each time interval, referred to as a frame, the scheduler may direct a remote station to transmit using frames which contain fixed length channels, i.e., synchronous, or variable length channels, i.e., asynchronous. In one mode, when data, such as digitized voice data or constant bit rate (CBR) data is to be transmitted, the data arrives at the transmitter at well-known intervals. Hence, the remote station transmission can be predicted and synchronous transmission is specified.

The duration of the frame is usually a trade off between the data throughput efficiency and the latency of the voice data. It is usually in the order of several milliseconds.

In a second mode, data may arrive in packets, for example, over the INTERNET, at unknown times, intervals or sizes, e.g., Internet Protocol (IP), then the output transmission cannot be predicated and the channel size or duration must be decided in real-time. Hence, the base station may choose one mode or the other for each individual remote station depending on the data traffic that will be managed. [0006] However, it may be necessary that both TDM and IP-based services be supported at a single base station. In these cases, the data of one service is configured to accommodate the format of the other service. For example, TDM systems may transport packet data services by allocating a constant bandwidth for the transmission of each packet. And in packet services, TDM or CBR services, e.g., voice-over-IP, may be encapsulated into packets and a synchronous transmission is allocated to those packets. However, the use of these mixed systems in disadvantageous as available resources are wasted either in overhead control information or the transmission of no informational data.

[0007] Hence, there is a need for a system that allows for the concurrent hybrid transmission of traditional TDM and IP-based services, which utilizes available bandwidth in an efficient manner.

Brief Description of the Drawings

[0008] Figure 1 illustrates a conventional TDMA point-to-multipoint wireless communication system;

[0009] Figure 2 illustrates a block diagram of a hybrid frame structure in accordance with the principles of the invention;

[0010] Figure 3 illustrates a flow chart of an exemplary process for allocating informational data in a hybrid frame in accordance with the principles of the invention;

[001 1] Figure 4 illustrates a flow chart of a second exemplary process for allocating informational data in a hybrid frame in accordance with the principles of the invention; and [0012] Figure 5 illustrates a system for operating on a hybrid frame in accordance with the principles of the invention.

[0013] Figures 1 through 5 and the accompanying detailed description contained herein are to be used as an illustrative embodiment of the present invention and should not be construed as the only manner of practicing the invention. It is to be understood that these drawings are for purposes of illustrating the concepts of the invention and are not to scale. It will be appreciated that the same reference numerals, possibly supplemented with reference characters where appropriate, have been used throughout to identify corresponding parts.

Detailed Description of the Invention

[0014] Figure 2 illustrates an exemplary embodiment of a hybrid frame 200 in accordance with the principles of the present invention. In this illustrated embodiment, the frame is divided into a TDM or CBR section 210 and a variable-length packet section 240.

[0015] TDM section 210 is divided into a plurality of conventional voice channels, represented as voice channels VCi, 212, VC₂, 214, and VCj, 216. VCi, 212, VC₂, 214, and VCj_, 216, as is known in the art, retain a constant position with respect to the beginning of the frame that allows for real-time, synchronous transmission of voice or audio data. Thus voice channels 212, 214, 216 provide a high transmission priority to voice or audio related information items at a fixed interval or rate to avoid delays in reception. Delays in reception of voice data are undesirable as they contribute to the reception of choppy and even unintelligible voice data. [0016] Variable section 240, representative of the remaining time within frame

200, contains variable length packet information items, represented as packet 1 , 242, packet 2, 244 and packet k 246. Packets 242, 244, 246, contain relatively lower priority data, e.g., computer-computer digital data, such as e-mail, that may be transmitted when time is available. In this case, the duration of each packet depends on the amount of data to be transmitted. Accordingly, the position of packet 244, for example, varies in relation to the beginning of the frame, depending upon the size of preceding packets. [0017] Figure 3 depicts a flow chart 300 of an exemplary process for determining the informational content of frame 200 of Figure 2. In this illustrative process, data, i.e., CBR and/or packet, to be transmitted in a frame is collected at block 310. At block 320, the data or as referred to data requests, are sorted based on a transmission priority. At block 330, a determination is made whether any data requests for real-time or constant bit rate data services are necessary.

[0018] If the answer is in the affirmative, then a request is assigned to one of the channels assigned to constant bit rate data portion of the frame at block 340. At block 350, a determination is made whether the CBR boundary maximum limit has been exceeded. In one aspect, the CBR boundary maximum limit is representative of a known number of channels. Hence, when the CBR boundary limit is exceeded each of the known number of channels has been assigned. In this case, the boundary insures part of the frame is reserved for allocating packet services.

[0019] If the answer is negative, then processing returns to block 330 to determine whether a next/subsequent CBR request is to be processed. [0020] ^' If, however, the answer is in the affirmative, then a determination is made at block 360, whether any requests for packet services were made. If the answer is in the affirmative, then a packet service is allocated to a portion of the packet service part of frame 200 at block 370.

[0021] At block 380, a determination is then made whether the frame has been filled. If the answer is negative then processing returns to block 360 to process the next packet service request.

[0022] If, however, the answer at block 380 is in the affirmative, then processing ends at block 390. Similarly, if the answer at block 360 is negative then processing ends at block 390.

[0023] Returning to the determination at block 330, i.e., any CBR requests made, if the answer is negative, then processing continues, at block 360, to determine whether packet data requests are available.

[0024] As will be understood, in this first exemplary embodiment, a frame may include unassigned voice channels or packets as the number of services required is insufficient to fill the frame. In this case, the unused or unallocated portions of the frame may be zero filled.

[0025] Figure 4 illustrates a flow chart of an exemplary process 400 in accordance with a second aspect of the invention. In this second aspect, requests for realtime and packet services within a current frame are collected at block 410. At block 420, the real-time and packet services requests are ordered based on a known priority. [0026] At block 430, determination is made whether a constant-bit-rate request service was made. If the answer is in the affirmative, than the data associated with a CBR request is assigned to a voice channel within the frame at block 440.

[0027] At block 450, a determination is made whether the frame time limit has been exceeded. If the answer is negative, then processing returns to block 430 to continue processing CBR requests.

[0028] If, however, the answer is in the affirmative, then processing is terminated at block 490 as no more time is available in the frame.

[0029] Returning to the determination at block 430, if the answer is negative, i.e., no more CBR requests, a determination is made at block 460, whether packet service requests have been made. If the answer is in the affirmative, then a packet data is allocated to the remaining portion of the frame at block 470.

[0030] At block 480, a determination is made whether the frame has been filled.

If the answer is negative, then processing returns to block 460 to process a next/subsequent packet service request. However, if the answer is in the affirmative, then processing is terminated at block 490.

[0031] Returning to the determination at block 460, if the answer is negative, then processing is terminated at block 490.

[0032] As will be understood, in this second exemplary process, the number of channels or fixed duration slots available for CBR data may vary, or may be dynamically allocated, based on the number of CBR requests made. Dynamic creation and allocation of the number of channels is advantageous as the frame utilization and efficiency are increased. Dynamic allocation is further advantageous as it allows for the hybrid frame to be used in a solely constant bit rate or solely packet service system. [0033] Figure 5 illustrates an exemplary system 500 for practicing the principles of the invention. In this exemplary system embodiment, input data, e.g., data requests, is received over network 550 and is processed in accordance with one or more software programs executed by processing system 510. The results of processing system 510 are then be transmitted over network 570.

[0034] More specifically, one or more input/output devices 540 receive input data from the illustrated sources 560 over network 550, which is then applied to processing system 510. Processing system 510 comprises processor 520 in communication with, at least, input/output device 540 and memory 530. Input/output devices 540, processor 520 and memory 530 may communicate over a communication medium 525. The communication medium 525 may represent one or more conventional communication buses, such as ISA, PCI, PCMCIA bus, a communication network, one or more internal connections of a circuit, circuit card or other device, as well as portions and combinations of these and other communication media. Processor 520 may be representative of one or more handheld calculators, special purpose or general purpose processing systems, desktop computers, laptop computers, palm computers, or personal digital assistant (PDA) device etc., as well as portions or combinations of these and other devices that can perform the operations illustrated in either Figure 3 or Figure 4. [0035] In a preferred embodiment, the execution of the operations illustrated in

Figures 3 or Figure 4 is implemented by computer readable code executed by processor 520. The code may be stored in the memory 530 or read/downloaded from a memory medium such as a CD-ROM or floppy disk (not shown).

[0036] The operations illustrated in Figures 3 or 4 may be performed sequentially or in parallel using different processors to determine specific values. Further, the data received by input/output device 540 may be immediately accessible by processor 520 or may be stored in memory 530. As will be appreciated, input/output device 540 may also allow for manual input, such as a keyboard or keypad entry or may read data from magnetic or optical medium.

[0037] In other embodiments, hardware circuitry may be used in place of, or in combination with, software instructions to implement the invention. For example, the elements illustrated herein may also be implemented as discrete hardware elements, which include software instructions, e.g., FPGA, PAL, ASIC, or may be integrated into a single unit.

[0038] System 500 may, as illustrated, transmit data over one or more network connections 570 from a server or servers over, e.g., a global computer communications network such as the Internet, Intranet, a wide area network (WAN), a metropolitan area network (MAN), a local area network (LAN), a terrestrial broadcast system, a cable network, a satellite network, a wireless network, or a telephone network (POTS), as well as portions or combinations of these and other types of networks.

[0039] While there has been shown, described, and pointed out, fundamental novel features of the present invention, it will be understood that various omissions and substitutions and changes in the apparatus described, in the form and details of the devices disclosed, and in their operation, may be made by those skilled in the art without departing from the spirit of the present invention to operate on other types of wireless communication protocols. It is expressly intended that all combinations of those elements which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated.

Claims

ClaimsWhat is claimed is:

1. In a wireless TDMA communication system, a method for generating a hybrid transmission frame having a known duration for concurrent audio and data transmission, said method comprising the steps of: prioritizing received data requests representative of said audio data and data transmission, wherein said audio data requests are assigned a high priority; allocating each of said audio data requests to one of a fixed duration channel within a first portion of said frame; and allocating said data transmission requests to a remaining portion of said frame.

2. The method as recited in claim 1, wherein said fixed duration channels are voice channels.

3. The method as recited in claim 1 , wherein said first portion is of a known duration.

4. The method as recited in claim 1, wherein said first portion is of a variable duration.

5. The method as recited in claim 3 wherein said first portion known duration is an integral number of said fixed duration channels.

6. The method as recited in claim 4 wherein said variable duration depends on a number of said audio data requests.

7. A hybrid transmission frame for a TDM communication system having a known duration comprising: a first section having a known number of fixed duration channels; and a second section occupying said remaining portion of said frame known duration.

8. The frame as recited in claim 7, wherein said fixed duration channels are voice channels.

9. The frame as recited in claim 7, wherein said first section known number of fixed duration channels is predetermined..

10. The frame as recited in claim 7, wherein said first section known number of fixed duration channels is variable.

1 1. The frame as recited in claim 10, wherein said variable number depends on a number of data requests.

12. The frame as recited in claim 1 1, wherein said data requests are selected from the group comprising: audio data, constant bit rate data.

13. The frame as recited in claim 1 wherein said known duration is selected from the group comprising a range between 2 and 10 milliseconds.

14. The frame as recited in claim 7 wherein said known duration is selected from the group comprising a range between 2 and 10 milliseconds.

15. In a wireless TDMA communication system, a system for generating a hybrid transmission frame having a known duration for concurrent audio and data transmission, said system comprising: a processor in communication with a memory operable to execute code for: receiving data requests representative of said audio when said audio data requests are available; receiving data requests representative of and data transmission when said data transmission requests are available; prioritizing said received data requests, wherein said audio data request are assigned a high priority; allocating each of said audio data requests to a fixed duration channel within a first portion of said frame; and allocating said data transmission requests to a remaining portion of said frame.

16. The system as recited in claim 15, wherein said fixed duration channels are voice channels.

17. The system as recited in claim 15, wherein said first portion is of a known duration.

18. The system as recited in claim 15, wherein said first portion is of a variable duration.

19. The system as recited in claim 17, wherein said first portion known duration is an integral number of said fixed duration channels.

20. The system as recited in claim 18 wherein said variable duration depends on a number of said audio data requests.

21. The system as recited in claim 15 wherein said audio data requests are representative of data selected from the group comprising: voice data, constant bit rate data.

22. The method as recited in claim 1 , wherein said audio data requests are representative of data selected from the group comprising: voice data, constant bit rate data.