GB2499633A

GB2499633A - Time-frequency resources are defined in a radio access network and sending opportunities are allocated for an apparatus to send a discovery message

Info

Publication number: GB2499633A
Application number: GB1203165.4A
Authority: GB
Inventors: Sami-Jukka Hakola; Samuli Turtinen; Anna Pantelidou; Timo Kalevi Koskela; Juha Pekka Karjalainen; Matti Pikkarainen; Ville Vartiainen
Original assignee: Renesas Mobile Corp
Current assignee: Renesas Electronics Corp
Priority date: 2012-02-23
Filing date: 2012-02-23
Publication date: 2013-08-28
Anticipated expiration: 2032-02-23
Also published as: GB201203165D0; GB2499633B

Abstract

The present application relates generally to Device to Device (D2D) communication in a radio access network (RAN) and seeks to use orthogonal radio channels in a discovery process that precedes a possible D2D communication. The RAN defines 201 a period consisting of k time-frequency resource chunks, each providing n sending opportunities on the orthogonal radio channels. Preferably, each of these n sending opportunities is usable on a different orthogonal radio channel. The period defined by the RAN comprises altogether k x n sending opportunities when k > 1, n is integer, and n > 2. Then, the RAN allocates 202 a first portion of the k x n sending opportunities to a first UE. The first UE needs at least one sending opportunity included in the first portion to send a discovery message in the discovery process. There may be a great number of simultaneous discovery processes, but the radio resources can be divided in a very flexible way between the discovery processes and other possible functions.

Description

1

A method and apparatus for using orthogonal radio channels

Technical Field

Embodiments of the present application relates generally to Device to Device 5 (D2D) communication in a radio access network (RAN). Universal Mobile Telecommunication System (UMTS), Universal Terrestrial Radio Access Network (UTRAN), a long term evolution (LTE) network called Evolved UTRAN (E-UTRAN), and an LTE advanced network are some examples of the RAN.

10 Background

Traditionally, terminals of a cellular network were able to communicate with each other only through base stations of the cellular network. In the other words, possibility to the D2D communication was missing. D2D communication is quite new technique in the radio access networks, but some patent applications exists of which 15 US 2009/0013081 and US 2009/0017797 represent the prior art for present application.

One current task of 3rd Generation Partnership Project (3GPP) is to develop LTE networks to fulfil demands of proximity-based applications. The proximity-based applications discover instances of the applications running in devices which are 20 capable to exchange data and close enough for the data exchange. This type of data exchange between the applications is an example of D2D communication. In public safety application the operation distance from a device to another device is at most 1 km and in other type of applications the operation distance is at most 100-200 m.

The D2D communication is utilized, for example, in social applications, local 25 advertising, multiplayer gaming, network offloading, and smart meters, which are described in the following. The social applications may exchange files, photos, text messages, etc., or the applications may provide Voice over IP (VoIP) conversation, one-way streaming video, or two-way video conference. The multiplayer gaming involves exchanging high resolution media between participants of a game and 30 transmission of control inputs from a participant's device to the other participants devices so that the correct causality of the control inputs of the all participants

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remains. The network offloading especially means that the device communicates directly with another device and thus saves the network resources on the radio access and core network level. The smart meters are low capability MTC (Machine-Type-Communication) devices that are used, for example, in vehicles.

5 A process in which a device tries to discover another communication device is termed a discovery process. During the discovery process the device emits a discovery signal and listens to discovery signals of other devices to find at least one device running an interesting application. With the discovery signal, the device basically informs its presence as well as its capabilities, running applications, and services that 10 it offers in proximity. Furthermore, the device may request the interesting service on discovery signal.

The discovery signal transmission is relatively simple to perform on given radio resources. A challenge arises when multiple devices are interested in the same device that has emitted a discovery signal. The challenge is then, how the radio 15 resources are allocated for the multiple devices that are simultaneously interested in sending their responses to the same device? A response to the discovery signal is termed a feedback signal. Collisions of the simultaneous feedback signals should be avoided as much as possible.

20 Summary

Some embodiments of the present invention aim to provide such advantage that radio resources can be divided in a very flexible way between a great number of simultaneous discovery processes and other functions. Thus, the discovery processes and the other functions may share the radio resources and utilize them in the same 25 time.

According to the invention there is provided a method for using orthogonal radio channels in a discovery process the method comprising the following to be performed in a radio access network:

defining a period consisting of k time-frequency resource chunks, each time-30 frequency resource chunk providing n sending opportunities, wherein the period comprises altogether £ x n sending opportunities when k > 1, n is integer, and n> 2,

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allocating a first portion of the k x n sending opportunities to a first user equipment, wherein the first user equipment needs at least one sending opportunity included in the first portion to send a discovery message in the discovery process.

In one embodiment the method further comprises the following to be 5 performed in the radio access network:

allowing use of at least one sending opportunity for sending a feedback message as response to the discovery message, wherein the at least one opportunity is included in the first portion and thus allocated to the first user equipment.

In one embodiment the method further comprises the following to be 10 performed in the radio access network:

requiring the first user equipment to disclose in the discovery message the at least one sending opportunity for the sending of the feedback message.

In one embodiment the method further comprises the following to be performed in the radio access network:

15 requiring the first user equipment to determine at least one such sending opportunity that is missing from the first portion.

allocating a second portion of the k x n sending opportunities to another user 20 equipment to be used in another discovery process.

In one embodiment, the certain type is one of the following types: a discovery type, a feedback type, a handshake type, an acknowledge type; and messages respective to the types are: a discovery message, a feedback message, a handshake message, and an acknowledgement message.

25 In one embodiment of the method m time-frequency resource chunks comprises (k x n) / m sending opportunities of the first portion so that each of the orthogonal radio channels is usable once among the (k * n) / m sending opportunities, 1 <m<k.

According to the invention there is also provided an apparatus, comprising: 30 a processing system arranged to cause the apparatus to perform in a radio access network at least the following:

4

defining a period consisting of k time-frequency resource chunks, each time-frequency resource chunk providing n sending opportunities, wherein the period comprises altogether k x n sending opportunities when k > 1, n is integer, and n > 2, and

5 allocating a first portion of the k x n sending opportunities to a first user equipment, wherein the first user equipment needs at least one sending opportunity included in the first portion to send a discovery message in the discovery process. In one embodiment the apparatus is further caused to perform:

allowing use of at least one sending opportunity for sending a feedback 10 message as response to the discovery message, wherein the at least one opportunity is included in the first portion and thus allocated to the first user equipment.

In one embodiment of the apparatus m time-frequency resource chunks comprises (k x n) / m sending opportunities of the first portion so that each of the orthogonal radio channels is usable once among the (£ x n) / m sending opportunities, 15 1 <m<k.

In one embodiment, the allocating is performed in response to arrival of the first user equipment to a cell of the radio access network.

In one embodiment, the allocating is performed in response to a resource request sent from the first user equipment.

20 In one embodiment, the apparatus is further caused to perform:

estimating a number of user equipments capable to receive the discovery message.

In one embodiment, the estimating is performed utilizing a discovery service register and user equipment position information available in the radio access 25 network.

In one embodiment, the apparatus is further caused to perform:

sending the estimated number to the first user equipment.

In one embodiment, the apparatus is further caused to perform:

determining a size of the first portion at least partly on the basis of the 30 estimated number.

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According to the invention, there is also provided a computer readable medium comprising a set of instructions, which, when executed on a radio access network causes the radio access network to perform the steps of:

defining a period consisting of k time-frequency resource chunks, each time-5 frequency resource chunk providing n sending opportunities, wherein the period comprises altogether k x n sending opportunities when k > 1, n is integer, and n> 2,

allocating a first portion of the k x n sending opportunities to a first user equipment, wherein the first user equipment needs at least one sending opportunity included in the first portion to send a discovery message in the discovery process. 10 Regarding to the three above-mentioned aspects and a set of embodiments, an embodiment described in the above in connection with one aspect, can also be used in another one of the three above-mentioned aspects. Regarding to the three following aspects and a set of embodiments in this summary, an embodiment described in the below in connection with one aspect, can also be used in another one of the three 15 following aspects.

According to the invention, there is also provided an apparatus, comprising: a processing system arranged to cause the apparatus to perform at least the following:

receiving a portion of the k x n sending opportunities sent from a radio access 20 network, wherein k stands for time-frequency resource chunks, each time-frequency resource chunk provides n sending opportunities, and wherein a period defined by the radio access network comprises altogether k x n sending opportunities, k > 1, n is integer, and n> 2,

using at least one sending opportunity included in the portion to send a 25 discovery message according to a discovery process.

In one embodiment the apparatus is further caused to perform:

preparing the discovery process by addressing a resource request to the radio access network and receiving the portion as response to the resource request.

30 In one embodiment the apparatus is further caused to perform:

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In one embodiment the apparatus is further caused to perform: 5 disclosing in the discovery message the at least one sending opportunity for the sending of the feedback message.

In one embodiment of the method in time-frequency resource chunks comprises (k x n) / m sending opportunities of the first portion so that each of the orthogonal radio channels is usable once among the (k * n) / m sending opportunities, 10 1 <m<k.

In one embodiment the apparatus is further caused to perform:

defining in the discovery message a length of the discovery process.

In one embodiment the apparatus is further caused to perform:

using at least one sending opportunity included in the first portion for 15 listening.

According to the invention there is also provided, a method for using orthogonal radio channels in a discovery process, the method comprising the following to be performed in an apparatus capable of operating in a radio access network:

20 receiving a portion of the k x n sending opportunities sent from a radio access network, wherein k stands for time-frequency resource chunks, each time-frequency resource chunk provides n sending opportunities, and wherein a period defined by the radio access network comprises altogether k x n sending opportunities, k > 1, n is integer, and n> 2, and

25 using at least one sending opportunity included in the portion to send a discovery message according to a discovery process.

According to the invention, there is also provided a computer readable medium comprising a set of instructions, which, when executed on an apparatus capable of operating in a radio access network causes the apparatus to perform the 30 steps of:

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receiving a portion of the k x n sending opportunities sent from a radio access network, wherein k stands for time-frequency resource chunks, each time-frequency resource chunk provides n sending opportunities, and wherein a period defined by the radio access network comprises altogether k x n sending opportunities, k > 1, n is 5 integer, and n> 2, and using at least one sending opportunity included in the portion to send a discovery message according to a discovery process.

Brief Description of the Drawings 10 For a more complete understanding of examples and embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:

FIGURE 1 shows an example of orthogonal radio channels and sending opportunities;

15 FIGURE 2 illustrates a method in one embodiment of the present invention,

the method controlling the use of orthogonal radio channels in a discovery process;

FIGURE 3 illustrates an apparatus in one embodiment of the present invention, the apparatus scheduling the use of orthogonal radio channels; and

FIGURE 4 illustrates an apparatus in one embodiment of the present 20 invention, the apparatus using the orthogonal radio channels.

Detailed Description

Generally speaking, a signal is detectable and measurable physical quantity or impulse, such as voltage, current, or magnetic field strength, by which a message or 25 information can be transmitted from one site to another. Thus, a discovery message is transmitted by the discovery signal and a feedback message is transmitted by the feedback signal. When a first UE sends the discovery message as a broadcast message and a second UE replies to it by sending the feedback message, the first UE and the second UE can be considered as communication parties. The communication between 30 the UEs is an application-specific and a user-specific subject matter. It is possible that the communication is very simple and includes only the discovery message and the

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feedback message. On the other hand, it is possible that the communication must be confirmed by using a handshake procedure and a real data transmission starts after the handshake procedure. The focus of the present application is on a discovery process that enables the communication between the UEs. In more detail, the present 5 application describes how to use orthogonal radio channels in the discovery process.

FIGURE 1 shows an example of the orthogonal radio channels and the sending opportunities provided by them. In this example each time-frequency resource chunk 101-107 comprises three sending opportunities, i.e. n = 3. The sending opportunities in the same time slot have different frequencies, thus n also defines a 10 number of different frequencies in one chunk. There are altogether nine orthogonal radio channels, in brief, channels. Numbers 1-9 marked in the chunks are channel numbers. For example, chunk 101 provides sending opportunities on channel 1, 2, and 3. Correspondingly, chunk 102 provides sending opportunities on channel 4, 5, and 6. Because k= 6, there is a set of six chunks 101-106 from which sending opportunities 15 can be allocated. When k = 6 and n = 3, there are k x n sending opportunities, i.e. 18 sending opportunities, usable in the six chunks. All 18 sending opportunities can be allocated to the same user equipment, or the sending opportunities can be allocated different user equipments. The symbol m discloses a number of chunks which is required to provide one sending opportunity on each channel. In this example m = 3, 20 because three chunks are required for all nine channels. A user equipment may use the first m chunks for sending a discovery message on all channels. Then the user equipment may listen during the next in chunks to all channels. If there are several possible senders of a feedback message, i.e. other user equipments, the user equipment may obtain, for example, nine chunks from the scheduler of the resource 25 pool. Then the user equipment may use the first m chunks for sending the discovery message and the rest 2 x m chunks for receiving possible feedback messages.

The symbol n is integer, but the symbols k and in may or may not be integers. Allocating of the sending opportunities is simpler when k and in are integers, but k could be, for example, 5 2A at which time the sending opportunity on channel 3 in 30 chunk 106 is still kept in the pool of radio resources.

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A method in accordance with an embodiment of the invention is performed in a radio access network (RAN). The method maybe performed in a base station of the RAN, such as eNodeB, or in some other apparatus coupled to the RAN. The radio resources, which the method controls, are sending opportunities on orthogonal radio 5 channels. The orthogonal radio channels may or may not be licensed to the operator of the RAN. An orthogonal radio channel to be used in the method is such that: a) an UE is able to emit a radio signal on the orthogonal radio channel and b) the quality of the UEs radio signal fulfils quality criterions and other general criterions. In addition, the orthogonal radio channel could be such that c) the UEs power consumption is low. 10 FIGURE 2 illustrates the method for controlling the use of orthogonal radio channels in a discovery process. When performing the method the RAN defines a period consisting of k time-frequency resource chunks, each time-frequency resource chunk providing n sending opportunities on n different orthogonal radio channels. The period defined by the RAN comprises altogether k* n sending opportunities when k > 15 1, n is integer, and n> 2. Then the RAN allocates a first portion of the k x n sending opportunities to a first UE. The first UE needs at least one sending opportunity included in the first portion to send a discovery message in the discovery process. When using Figure 1 as an example, the size of the first portion may be 1-18 sending opportunities. The remaining sending opportunities, which are not allocated to the 20 first UE, may be used in another discovery process.

The first portion may or may not include sending opportunities of each chunk. The k chunks may include a chunk, which is entirely allocated to the first UE, and another chunk of which no sending opportunity is allocated to the first UE. It is also possible to allocate a portion of a chunk to the first UE. For example, the allocation 25 can be performed so that a) one sending opportunity of the three sending opportunities of a chunk is allocated to the first UE and b) every fifth chunk includes a single sending opportunity intended for the first UE. In this example, the first UE obtains one sending opportunity from the fifth, tenth, and fifteenth chunks, when k = 15 and the numbering starts from 1.

30 The before-mentioned step of defining the period and the step of allocating the first portion are the main steps of the method. The other steps of the method are

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beneficial options. One beneficial option is that the RAN allows a second UE to send, a response to the discovery message, a feedback message by using at least one sending opportunity that is included in the first portion and thus allocated to the first UE. In other words, the first UE reallocates to other UEs those sending opportunities 5 which the RAN has allocated to it. For example, the first UE can list in a discovery message all the sending opportunities which it has not yet used. Then possible recipients of the discovery message, i.e. the other UEs, are allowed to pick from the list sending opportunities for sending a feedback message to the first UE.

Listing the sending opportunities in the discovery message is just one way to 10 inform the other UEs how to respond the discovery message. Alternatively, the RAN requires that the second UE determines the at least one sending opportunity.

Basically, there are a number of possible determination mechanisms for determining one or more sending opportunities. Two preferable determination mechanisms are described in the following.

15 One determination mechanism is based on detecting periods among time-

frequency resource chunks. Such period comprises m time-frequency resource chunks, 1 < m < k. Those in chunks comprises {k* ri) I m sending opportunities so that each of the orthogonal radio channels is usable exactly once among the (k x n) / m sending opportunities. The first UE has allocated, for example, 2 x m chunks and the first UE 20 uses the first m chunks for sending the discovery message, i.e. the first UE sends its discovery message on the all orthogonal radio channels. Then, during the next m chunks, the first UE listens to the all orthogonal radio channels. The other UEs are able to determine that the first UE is listening and next in chunks are intended for replying the discovery message. This determination may be based on the number of 25 chunks which the first UE has included in its discovery message. If there are number of UEs, collisions are possible. A collision occurs, if two or more UEs use the same sending opportunity. Thus, the other UEs pick randomly two sending opportunities among all the sending opportunities included in the next in chunks, and each of them sends its feedback message using the two picked sending opportunities. 30 Another determination mechanism is also based on detecting periods among time-frequency resource chunks. In addition, it is based on scheduling. The RAN

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schedules the channels so that there are approximately a same number of listeners on each channel, after which the RAN requires each UE to listen a certain orthogonal channel. When the first UE sends the discovery message on the all orthogonal channels, there is no need to listen to more than one channel, which saves the battery 5 of the listening UE. In this other determination mechanism the second UE sends the feedback message during the next in chunks using the channel on which it received the discovery message. The second UE selects, on the basis of the channel, the sending opportunity among the (k x n) / m sending opportunities. Thus, the same channel is used for sending and receiving discovery messages.

10 In both determination mechanisms the discovery process is synchronized. In one option, the sending opportunities are usable for a certain type of message, wherein the certain type is one of the following types: a discovery type, a feedback type, a handshake type, an acknowledge type. The messages respective to the types are: a discovery message, a feedback message, a handshake message, and an 15 acknowledgement message. The discovery message and the feedback message are already discussed in the above. The acknowledgement message indicates to the second UE that the first UE has received the feedback message sent by the second UE. Then the second UE stops sending its feedback message and waits to the end of the discovery period whether the first UE sends the handshake message or not. If the 20 first UE sends the handshake message, the first UE has selected the second UE to start D2D communication.

As described in the above, the first UE can reallocate its sending opportunities to other UEs. In addition or alternatively, the other UEs may obtain sending opportunities from the RAN. In one option an UE receives sending opportunities from 25 an eNodeB when it arrives to the cell of the eNodeB. In other words, the eNodeB sends the sending opportunities without a request by the UE. In another option the UE receives the sending opportunities only when requesting them from the eNodeB.

FIGURE 3 shows the apparatus scheduling the use of orthogonal radio channels. The apparatus is located in the RAN and it may be termed, for example, a 30 scheduler or an eNodeB. The apparatus 301 comprises at least one processor 302 and at least one memory 303 including computer program code. The apparatus 301

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defines a period consisting of k time-frequency resource chunks, each time-frequency resource chunk providing n sending opportunities on n different orthogonal radio channels, wherein the period comprises altogether k x n sending opportunities when k > 1, n is integer, and n > 2. Then the apparatus 301 allocates a first portion 304 of the 5 £ x n sending opportunities 305 to a first UE.

In one embodiment of the invention the apparatus 301 is arranged to perform the all steps of the method described in the above.

In one option the apparatus 301 estimates a number of user equipments capable to receive the discovery message sent by the first UE. Assuming that the user 10 equipments include Global Positioning System (GPS) devices, they could send their position information via the radio access network to the apparatus 301 to be processed there, but preferably the apparatus 301 estimates the number of the user equipments as follows. The apparatus 301 utilizes the user equipment position information available in the RAN. The RAN receives continuously UE-specific information about a cell, 15 and a sector inside the cell, in which each UE is currently located. Timing advance information and sector information are a basis for quite accurate position estimates. When the apparatus 301 has calculated the current position of the first UE and the current positions of user equipments locating in proximity of the first UE, the calculation results in a set of UEs. This set can be termed "proximity UEs". Then the 20 apparatus 301 interrogates from the discovery service registers which UEs of those proximity UEs are registered in the service? The apparatus 301 omits an UE among the proximity UEs, if the UE is not registered in the service. Finally, the apparatus 301 calculates the number of the proximity UEs, i.e. the UEs that are still included in the set.

25 In one option, the apparatus 301 allocates sending opportunities to the first UE

when the first UE arrivals to a cell of the radio access network.

Alternatively, the apparatus 301 performs the allocation in response to a resource request sent from the first user equipment. When using this option, the apparatus 301 preferably sends the number of the proximity UEs to the first UE. Then 30 the first UE forms its resource request, taking into account the number of the proximity UEs, to and addresses the resource request to the apparatus 301. The

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apparatus 301 may or may not allocate sending opportunities in accordance with the resource request.

Then the apparatus 301 determinates a size of the first portion 304 on the basis of this number. The apparatus may estimate, for example, that the user equipments 5 need two sending opportunities per UE to send their feedback messages to the first UE.

FIGURE 4 shows an apparatus 401 for using the orthogonal radio channels. The apparatus is a user equipment or a part of it. The apparatus 401 comprises at least one processor 402 and at least one memory 403 including computer program code. 10 The apparatus 401 is capable to receive a portion 404 of the k * n sending opportunities sent from a radio access network, wherein k stands for time-frequency resource chunks, each time-frequency resource chunk provides n sending opportunities on n different orthogonal radio channels. A period defined by the radio access network comprises altogether k x n sending opportunities, k > 1, n is integer, 15 and n > 2. In a discovery process the apparatus 401 uses at least one sending opportunity included in the portion to send a discovery message 405.

In one option the apparatus 401 prepares the discovery process by addressing a resource request to the radio access network and then receiving the portion 404 as response to the resource request.

20 In one option the apparatus 401 assists possible recipients of the discovery message by disclosing in the discovery message the at least one sending opportunity for the second user equipment.

In one option the apparatus 401 assists the possible recipients of the discovery message by defining in the discovery message a length of the discovery process. 25 The exemplary embodiments described in the above may include, for example,

any suitable network devices, base stations, eNodeBs, RAN devices, laptop computers, Internet appliances, handheld devices, cellular telephones, smart phones, wireless devices, and the like, capable of performing the processes of the exemplary embodiments. The devices and subsystems of the exemplary embodiments can 30 communicate with each other using any suitable protocol and they may be implemented using one or more programmed computer systems or devices.

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The present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The application logic, software or instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "computer-readable 5 medium" may be any media or means that contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer-readable medium may comprise a computer-readable storage medium that may be any media or means that contain or store the instructions for use by or in connection with an instruction 10 execution system, apparatus, or device, such as a computer.

The exemplary embodiments can store information relating to various processes described herein. This information can be stored in one or more memories, such as a hard disk, optical disk, magneto-optical disk, RAM, and the like.

All or a portion of the exemplary embodiments can be conveniently 15 implemented using one or more general purpose processors, microprocessors, digital signal processors, micro-controllers, and the like, programmed according to the teachings of the exemplary embodiments of the present invention, as will be appreciated by those skilled in the computer and/or software art(s). Appropriate software can be readily prepared by programmers of ordinary skill based on the 20 teachings of the exemplary embodiments, as will be appreciated by those skilled in the software art. In addition, the exemplary embodiments can be implemented by the preparation of application-specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be appreciated by those skilled in the electrical art(s). Thus, the exemplary embodiments are not limited 25 to any specific combination of hardware and/or software.

Stored on any one or on a combination of computer readable media, the exemplary embodiments of the present invention can include software for controlling the components of the exemplary embodiments, for driving the components of the exemplary embodiments, for enabling the components of the exemplary embodiments 30 to interact with a human user, and the like. Such software can include, but is not limited to, device drivers, firmware, operating systems, development tools,

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applications software, and the like. Such computer readable media further can include the computer program of an embodiment of the present invention for performing all or a portion (if processing is distributed) of the processing performed in implementing the present invention. Computer code devices of the exemplary embodiments of the 5 present invention can include any suitable interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs), Java classes and applets, complete executable programs, Common Object Request Broker Architecture (CORBA) objects, and the like.

While the present invention has been described in connection with a number 10 of exemplary embodiments, and implementations, the present invention is not so limited, but rather covers various modifications, and equivalent arrangements, which fall within the purview of prospective claims.

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Claims

Claims

1. A method for using orthogonal radio channels in a discovery process, the method comprising the following to be performed in a radio access network:

5 defining a period consisting of k time-frequency resource chunks, each time-frequency resource chunk providing n sending opportunities, wherein the period comprises altogether k x n sending opportunities when k > 1, n is integer, and n> 2,

allocating a first portion of the k x n sending opportunities to a first user equipment, wherein the first user equipment needs at least one sending 10 opportunity included in the first portion to send a discovery message in the discovery process.

2. The method according to claim 1, wherein the method further comprises the following to be performed in the radio access network:

15 allowing use of at least one sending opportunity for sending a feedback message as a response to the discovery message, wherein the at least one opportunity is included in the first portion and thus allocated to the first user equipment.

3. The method according to claim 2, wherein the method further 20 comprises the following to be performed in the radio access network:

requiring the first user equipment to disclose in the discovery message the at least one sending opportunity for the sending of the feedback message.

4. The method according to any of claims 1 to 3, wherein the method 25 further comprises the following to be performed in the radio access network:

requiring the first user equipment to determine at least one such sending opportunity that is missing from the first portion.

5. The method according to claim 2, wherein the method further 30 comprises the following to be performed in the radio access network:

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allocating a second portion of the k x n sending opportunities to another user equipment be used in another discovery process.

6. The method according to any of claims 1 to 5, when k> 2, and wherein 5 at least one chunk of the k time-frequency resource chunks is usable only for a certain type of message.

7. The method according to claim 6, wherein the certain type is one of the following types:

10 a discovery type, a feedback type, a handshake type, an acknowledge type;

and messages respective to the types are:

a discovery message, a feedback message, a handshake message, and an acknowledgement message.

15

8. The method according to any of claims 1 to 7, wherein m time-frequency resource chunks comprises (k x n) / m sending opportunities of the first portion so that each of the orthogonal radio channels is usable once among the (k x n) / in sending opportunities, I < in < k.

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9. An apparatus, comprising:

a processing system arranged to cause the apparatus to perform in a radio access network at least the following:

defining a period consisting of k time-frequency resource chunks, each

25 time-frequency resource chunk providing n sending opportunities, wherein the period comprises altogether k x n sending opportunities when k > 1, n is integer, and n > 2, and allocating a first portion of the k x n sending opportunities to a first user equipment, wherein the first user equipment needs at least one sending

30 opportunity included in the first portion to send a discovery message in the discovery process.

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10. The apparatus according to claim 9, wherein the apparatus is further caused to perform:

allowing use of at least one sending opportunity for sending a feedback 5 message as a response to the discovery message, wherein the at least one opportunity is included in the first portion and thus allocated to the first user equipment.

11. The apparatus according to claim 9 or 10, wherein in time-frequency resource chunks comprises (k * n) / m sending opportunities of the first portion so that

10 each of the orthogonal radio channels is usable once among the (k x n) / m sending opportunities, 1 < in < k.

12. The apparatus according to any of claims 9 to 11, wherein the allocating is performed in response to arrival of the first user equipment to a cell of

15 the radio access network.

13. The apparatus according to any of claims 9 to 11, wherein the allocating is performed in response to a resource request sent from the first user equipment.

20

14. The apparatus according to any of claims 9 to 13, wherein the apparatus is further caused to perform:

estimating a number of user equipments capable to receive the discovery message.

25

15. The apparatus according to claim 14, wherein the estimating is performed utilizing a discovery service register and user equipment position information available in the radio access network.

30 16. The apparatus according to claim 14 or 15, wherein the apparatus is further caused to perform:

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sending the number to the first user equipment.

17. The apparatus according to claim 14, 15 or 16, wherein the apparatus is caused to perform:

determining a size of the first portion at least partly on the basis of the number.

18. An apparatus, comprising:

a processing system arranged to cause the apparatus to perform at least the following:

receiving a portion of the k x n sending opportunities sent from a radio access network, wherein k stands for time-frequency resource chunks, each time-frequency resource chunk provides n sending opportunities, and wherein a period defined by the radio access network comprises altogether k * n sending opportunities, k > 1, n is integer, and n > 2, and using at least one sending opportunity included in the portion to send a discovery message according to a discovery process.

19. The apparatus according to claim 18, wherein the apparatus is further caused to perform:

preparing the discovery process by addressing a resource request to the radio access network and receiving the portion as response to the resource request.

20. The apparatus according to claim 18 or 19, wherein the apparatus is further caused to perform:

allowing use of at least one sending opportunity for sending a feedback message as response to the discovery message, wherein the at least one opportunity is included in the first portion and thus allocated to the first user equipment.

20

21. The apparatus according to any of claims 18 to 20, wherein the apparatus is caused further to perform:

disclosing in the discovery message the at least one sending opportunity for the sending of the feedback message.

5

22. The apparatus according to any of claims 18 to 21, wherein in time-frequency resource chunks comprises (k x n) / m sending opportunities of the first portion so that each of the orthogonal radio channels is usable once among the (k x n) / in sending opportunities, I < in < k.

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23. The apparatus according to any of claims 18 to 22, wherein the apparatus is further caused to perform:

defining in the discovery message a length of the discovery process.

15 24. The apparatus according to any of claims 18 to 23, wherein the apparatus is further caused to perform:

using at least one sending opportunity included in the first portion for listening.

20 25. A computer readable medium comprising a set of instructions, which,

when executed on a radio access network causes the radio access network to implement the method of any of claims 1 to 8.

26. A method for use of orthogonal radio channels in a discovery process,

25 the method comprising the following to be performed in an apparatus capable to operate in a radio access network:

receiving a portion of the k x n sending opportunities sent from a radio access network, wherein k stands for time-frequency resource chunks, each time-frequency resource chunk provides n sending opportunities, and wherein a period

30 defined by the radio access network comprises altogether k* n sending opportunities, k > 1, n is integer, and n > 2, and

21

using at least one sending opportunity included in the portion to send a discovery message according to a discovery process.

27. A computer readable medium comprising a set of instructions, which, when 5 executed on an apparatus capable of operating in a radio access network causes the apparatus to implement the method of claim 26.