GB2545424A - Methods and devices for DMG link establishment in millimeter wave communication networks - Google Patents

Abstract

In 802.11ad networks, Directional Multi-Gigabit DMG links can be established between two stations with bandwidth allocation that can become insufficient as the stations move relatively one to each other and a degraded coding scheme is selected. To avoid useless bandwidth to be allocated and thus wasted, the present invention improves the control of DMG link establishment. A sector sweep, SSW, phase is performed between the two stations enabling the initiating station to determine a first Transport Specification TSPEC and send it to the second station. The second station thus determines a second TSPEC and a quality threshold taking into account its own requirements and mobility margins and transmits to the first station. The initiating station can trigger the establishment of a DMG link with the other station based on the second TSPEC, only if the quality threshold is measured during a subsequent SSW phase. A DMG link is thus not automatically established as conventionally performed.

Description

METHODS AND DEVICES FOR DMG LINK ESTABLISHEMENT IN MILLIMETER WAVE COMMUNICATION NETWORKS

FIELD OF THE INVENTION

The present invention relates generally to the domain of millimeter-wave wireless communication and, more particularly, to techniques for further controlling the establishment of a directional link, such as a DMG (standing for “Directional Multi-Gigabits”) link, in order to avoid wasting bandwidth.

The invention finds application in 802.11 ad-compliant wireless communication networks.

BACKGROUND OF THE INVENTION

Current Wireless Gigabit Alliance (WiGig) and Institute of Electrical and Electronics Engineers (IEEE) 802.11ad specifications define a 60GHz system in which all the stations use the same basic channel bandwidth for both transmission and reception.

The 60GHz band is an unlicensed band which features a large amount of bandwidth (up to 7 GHz) and a large worldwide overlap, which cannot be achieved by WLAN standard stations using 2.4GHz and 5GHz radio bands.

The large bandwidth means that a very high volume of information can be transmitted wirelessly. As a result, multiple applications that require transmission of a large amount of data, for instance quasi lossless compressed video streaming about 300 Mbps to 1 Gbps, can be developed to allow wireless communication around the 60GHz band within short distances. Examples of such applications include, but are not limited to, wireless high definition TV (HDTV), wireless docking stations, wireless Gigabit Ethernet, and many others. Wireless local area network (WLAN) standards, such as WiGig Alliance (WGA) and IEEE 802.11 ad, are being developed to serve applications that utilize the 60 GHz spectrum.

The 802.11ad specifications define ’Medium Access Control’ MAC and 'Physical Layer’ PHY specifications requirements that provide access to the wireless medium.

The millimetre-wave communication presents a link budget issue due to high path losses that are inherent to high-frequency bands. Thus, the carrier signals in the 60GHz band are subject to path losses which are at least 20dB worse than in the 5GHz band.

This high degradation due to the high frequency of the carrier signal is usually mitigated by using a small size array of antennas realized by small size antenna elements. Such an antenna array focuses the beam of the transmitting and receiving antennas, such that the transmitter-receiver channel's SNR or signal-to-interference, together with the noise on the channel, is maximized, thereby compensating the path losses. Such focusing antenna arrays are named “directional antennas”.

This optimization of antenna directions depends on the physical locations of the transmitter, the receiver, and other objects located between the receiver and the transmitter.

The 802.11ad specifications define a specific communication protocol, named DMG for “Directional Multi-Gigabits”, which is applicable to millimetre-wave communication only.

The DMG protocol is able to manage directional antenna training for low data rate communication, around 25 Mbps using a Common Mode Signaling, CMS, required to manage the 802.11 ad stations in the network.

Additionally, the DMG protocol makes it possible to establish high data rate links, achieving up to 7 Gbps data rate, by controlling simultaneously the transmitter antenna beamforming and the receiver antenna beamforming.

As defined in 802.11 ad, beamforming is a mechanism that is used by a pair of stations, namely an initiating station and a responding station, to achieve the necessary DMG link budget for subsequent communication. Beamforming (BF) training is a bidirectional sequence of BF training frame transmissions that uses sector sweep and provides the necessary signaling to allow each station to determine appropriate antenna system settings for both transmission and reception. After the successful completion of beamforming training, beamforming is said to be established.

Next, high data rate transfer can be performed on the established link by reserving bandwidth on the 60GHz network and thus transmitting data. To do so, the transmitter requests a control point (also known as Personal basic service set Control Point or PCP) or access point (AP) of the 60GHz network for a time period to support its need. This request usually provides a so-called traffic specification (TSPEC) which describes traffic characteristics and thus required allocation.

In practice, the data rate achievable between two stations can vary from low data rates, such as 25Mbps, to very high data rates, such as 7Gbps, over about ten meters distance. Figure 1 illustrates various data rates that can be achieved depending on the distance between the two stations. Each possible data rate is associated with a modulation and coding scheme, MCS, which defines a constellation configuration and a code rate for transmitting millimeter-wave signals. Selecting a data rate thus means selecting a corresponding MCS.

In the DMG protocol, the decision regarding which MCS to be utilized is based on the traffic specification, and made to support a low packet error rate, less than 1% in amendment 802.11 ad, for the upper layer to the MAC.

However, because the physical channel changes and the stations can move from time to time, the selected data rate and thus selected MCS is adapted over the time, to keep the packet error criteria (1%) and data rate required by the station which sent the traffic specification to initiate the data link. Thus, the MCS selection process is re-performed when a new MCS needs to be selected.

Selection of MCS is for instance described in US 2014/185551. Antenna training is performed to select an MCS and corresponding data rate, and re-training of the antenna is performed upon triggering events such as loss of reliability in a radio link or such as failing to select an appropriate MCS.

However, due to the changes in MCS responsive to station movements, the time period initially allocated by the AP/PCP may become insufficient to achieve end-to-end link quality, in particular because the MCS and thus the corresponding data rate may have decreased while the time period remains unchanged. Such issue appears at each boundary of the DMG data rates (i.e. each MCS except basic MCSO).

Lower data rate (or MCS) with a maintained allocated time period means that less bandwidth is available. A result is poor data quality transmission between the stations, due to a higher number of packets discarded and to more errors. The transmitted may even be unusable, in which case the bandwidth used has been lost for the overall network.

SUMMARY OF INVENTION

It is a broad objective of the present invention to improve this situation. A goal of embodiments of the invention is to seek for avoiding the establishment of such a directional link usually a high data rate or DMG link, when conditions of link quality cannot be achieved.

Another goal of embodiments of the invention is to establish a directional link that mirrors the stations’ needs more closely.

Yet, another goal of embodiments of the invention is to provide control when establishing a directional link in order to avoid wasting bandwidth.

Yet, another goal of embodiments of the invention is to provide a preventive mechanism to establish a directional link, in order to anticipate stations’ needs.

The present invention has been devised to overcome one or more foregoing limitations.

In this context, first embodiments of the invention provide a method performed by an initiating station having an antenna operating in a millimeter-wave communication network, e.g. a personal basic service set (DMG BSS) according to 802.11 ad, managed by a control or access point, comprising the following steps: performing an antenna training with a responding station and determining, based on a result (usually an SNR or RCPI of the responding station) of the antenna training, a first traffic specification defining traffic characteristics for a directional link; sending the determined first traffic specification to the responding station, and responsive to the sending, receiving a second traffic specification from the responding station; and performing, with the control or access point, a bandwidth allocation of a directional link, using the second traffic specification.

From the responding station’s perspective, the first embodiments of the invention provide a method performed by a responding station having an antenna operating in a millimeter-wave communication network managed by a control or access point, comprising the following steps: performing an antenna training with an initiating station (which training usually provides metrics such as an SNR or RCPI of the responding station), and subsequent to the antenna training, receiving a first traffic specification from the initiating station; determining, based on the first traffic specification, a second traffic specification defining traffic characteristics for a directional link; sending the determined second traffic specification to the initiating station for the latter to perform, with the control or access point, a bandwidth allocation of a directional link, using the second traffic specification.

Note that the responding station preferably determines the second traffic specification taking into account its own needs. The initiating station may be either one of a transmitting station, a receiving station and a third-party station.

The exchange of the first and second TSPEC between the two stations according to the first embodiments appears as a link negotiation between them. Such exchange does not exist in the know prior art, prior to establishing a directional link, such as a DMG link.

These embodiments make it possible for the use of bandwidth and user experience to be improved.

This is achieved by this exchange since the responding station can thus provide its point of view (i.e. its needs) through the second TSPEC, which in turns makes it possible to instantly establish a directional link that meets both stations’ needs.

Indeed, link quality estimation by the responding station seems more precise than one estimation by the initiating station, taking benefit of the knowledge of the first TSPEC from the initiation station, and of its characteristics including its directional antenna gain and its receiver sensitivity according to each available MCS.

Correspondingly, the first embodiments of the invention provide an initiating station having an antenna operating in a millimeter-wave communication network, e.g. a personal basic service set (DMG BSS) according to 802.11 ad, managed by a control or access point, comprising: an antenna training module configured to perform an antenna training with a responding station; a traffic specification module configured to determine, based on a result (usually an SNR or RCPI of the responding station) of the antenna training, a first traffic specification defining traffic characteristics for a directional link; a communication interface configured to send the determined first traffic specification to the responding station, and responsive to the sending, to receive a second traffic specification from the responding station; and a bandwidth allocation module configured to perform, with the control or access point, a bandwidth allocation of a directional link, using the second traffic specification.

From the responding station’s perspective, the first embodiments of the invention provide a responding station having an antenna operating in a millimeter-wave communication network managed by a control or access point, comprising: an antenna training module configured to perform an antenna training with an initiating station (which training usually provides metrics such as an SNR or RCPI of the responding station), a communication interface configured to receive, subsequently to the antenna training, a first traffic specification from the initiating station; a traffic specification module configured to determine, based on the first traffic specification, a second traffic specification defining traffic characteristics for a directional link; the communication interface being further configured to send the determined second traffic specification to the initiating station for the latter to perform, with the control or access point, a bandwidth allocation of a directional link, using the second traffic specification.

The initiating and responding stations have the same advantages as those defined above with respect to the methods according to the first embodiments.

Optional features of embodiments of the invention are defined in the appended claims. Some of these features are explained here below with reference to a method, while they can be transposed into system features dedicated to any station according to embodiments of the invention.

In some embodiments, the second traffic specification is sent or received from the responding station together with a link quality threshold as a condition to be reached by the directional link for the initiating station to trigger the bandwidth allocation with the control or access point.

Thanks to the threshold, a directional link is not always established as in the prior art. On the contrary, a directional link is established when link reliability can be achieved. It results that loss of bandwidth for the overall network (i.e. useless allocation and low performance schemes) is avoided when conditions of link quality cannot be achieved for instance (as defined in the threshold).

In addition, user experience is improved because the artefacts due to moving over MCS quality boundaries are limited.

Note that the link quality threshold is a feedback from the responding station to the initiating station to indicate one or more conditions to trigger bandwidth allocation according to changes over time.

According to specific embodiments, the link quality threshold is based on an antenna gain, RX_ANT_GAIN_STA2, of the responding station (usually in directional and receiving mode along the best sector determined in the beamforming training) and on a mobility gain margin, MOB_GAIN. The triggering condition thus mirrors responding station’s requirements while providing a margin to allow relative mobility of the two stations within the network.

According to a specific feature, the link quality threshold RCPIt is determined using the following formula RCPIt= RCPI_MCSy-RX_ANT_GAIN_STA2 + MOB_GAIN, where RCPI_MCSy is a signal quality metric associated with a modulation and coding scheme, MCSy, determined by the responding station from the second traffic specification. Such link quality threshold, for instance of the received-channel-power-indicator type, RCPI type, may thus be easily used for comparison with RCPI of each MCS at the initiating station.

In specific embodiments, the method at the initiating station may further comprise determining whether or not a reception quality obtained by the initiating station during a sector sweep phase with the responding station after the second traffic specification is received, satisfies the link quality threshold, and only in case of positive determining, performing the bandwidth allocation step with the control or access point.

In particular, the obtained reception quality may be a received power level RCPI2 of the responding station as received by the initiating station from the responding station during the sector sweep phase.

In specific embodiments, the method at the initiating station may further comprise determining whether or not a directional link complying with the second traffic specification satisfies the link quality threshold, and only in case of positive determining, performing the bandwidth allocation step with the control or access point.

For instance, the link quality threshold is satisfied when the initiating station can select an MCS that both complies with the data rate specified in the second TSPEC and has a better RCPI or the like compared to the link quality threshold. Indeed, it is assumed that the responding station keeps the second TSPEC compliant with the needs defined in the first TSPEC (it is to be sure that the initiating station can transmit data at least as originally requested in the first TSPEC).

According to a specific feature, in case of negative determining, the method at the initiating station further comprises performing an antenna re-training. This is to monitor the evolving of network configuration over the time to establish a directional link only when the required link quality is achieved.

In some embodiments, the first traffic specification is sent using a directional mode of the antenna determined during the antenna training and the second traffic specification is received using an omnidirectional mode of the antenna.

Symmetrically from the responding station’s perspective, the first traffic specification is received using an omnidirectional mode of the antenna, and the second traffic specification is sent using a directional mode of the antenna determined during the antenna training.

These provisions show that the link negotiation through exchange of the traffic specifications takes place before the two stations are able to communicate at high data rate. This is because high data rate configuration is conventionally obtained only through a beam refinement protocol that is performed after accessing a time period reserved with the control or access point. And the link negotiation takes place before requesting said control or access point to allocate bandwidth.

In some embodiments, the second traffic specification is different from the first traffic specification. This is to take into account responding station’s needs. A directional link different from that would be obtained using prior art is thus established, in particular having a TSPEC adapted to not only the initiator’s requirements, but also to the responder’s requirements.

In specific embodiments, the second traffic specification includes an adjusted increased data rate compared to a data rate defined in the first traffic specification, and/or an adjusted increased time allocation compared to a time allocation defined in the first traffic specification. Such adjusting steps are performed by the responding station when determining the second TSPEC. Thanks to such increasing of data rate and/or time allocation, the responding station keeps the second TSPEC compliant with the needs defined in the first TSPEC. This is to be sure that the initiating station can still transmit data as originally requested in the first TSPEC, as soon as a directional link is established according to the invention.

Note that in the standard 802.11ad, the time allocation is combined with a type of access to form a so-called traffic specification. As a consequence, a traffic specification in the meaning of the invention may include a standardized traffic specification as defined in 802.11 ad together with a data rate.

In some embodiments, the adjusted increased data rate and/or the adjusted increased time allocation is or are determined by the responding station based on a maximum allowable bandwidth, a spare bandwidth to keep for one or more other stations, an overall bandwidth shared with one or more other stations, a mobility margin (e g. degrading an MCS level inferred from TSPEC1 by one level) and/or a duplex or relay or multi-copy requirement of data traffic between the two stations. This approach takes into account actual requirements to make the TSPEC evolving.

For instance, a maximum allowable bandwidth or time allocation can be allocated to a particular allocation. For illustrative purposes, in case of a duplex link, the maximum time allocation can be limited to 50% of the overall available time for one way (upstream) of the duplex transmission in order to permit to allocate an equivalent time to the second way (downstream).

The same can be applied to a communication involving a relay. The overall time allocation can be shared into two time allocations: a first time allocation for the data transmission from the source to the relay, and a second time allocation for the data transmission from the relay to the destination.

Also, the time allocation may be limited to a maximum value to enable further link establishment.

In other embodiments, the antenna training includes a sector sweep phase to discover a best antenna sector for each of the initiating station and the responding station. The SSW is preferably performed at low data rate, below 50 Mbps.

In other embodiments, the result of the antenna training and the link quality threshold, if any, include a metric value of an antenna signal reception quality. For instance, the metric value may be one of a signal-to-noise ratio, SNR, level and a received channel power indicator, RCPI. Handling such type of link quality threshold requires low complex processing for the stations.

In some embodiments, the first and second traffic specifications include a data rate defining a data rate requirement and include a time allocation defining a bandwidth requirement. As conventionally known, the TSPEC may also indicate a traffic type and usage (e.g. UDP/RTP or TCP, and duplex or simplex). These items of information may be efficiently updated by the responding station in order to control and trigger the establishment of the directional link.

In some embodiments, the method further comprises using the allocated bandwidth of the directional link to exchange data with the responding/initiating station. Actual transmission of data may thus occur. It is reminded that the initiating station may be either one of a transmitting station, a receiving station and a third-party station. The responding station may thus be a transmitting station as well.

In some embodiments, the millimeter-wave communication network operates over a 60Ghz band in accordance to IEEE 802.11ad standard. In such situation, the directional link may be a DMG link in the meaning of same standard.

Another aspect of the invention relates to a millimeter-wave communication system having a control or access point and at least two stations according to respectively an initiating station as defined above and a responding station as defined above, establishing a directional link between them.

Another aspect of the invention relates to a non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a station device of a millimeter-wave communication network, causes the station device to perform any method as defined above.

The non-transitory computer-readable medium may have features and advantages that are analogous to those set out above and below in relation to the methods and node devices.

Another aspect of the invention relates to a method in a millimeter-wave communication network managed by a control or access point, substantially as herein described with reference to, and as shown in, Figure 4, or Figure 5a, or Figure 5b, or Figures 4, 5a and 5b of the accompanying drawings.

At least parts of the methods according to the invention may be computer implemented. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit", "module" or "system". Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer usable program code embodied in the medium.

Since the present invention can be implemented in software, the present invention can be embodied as computer readable code for provision to a programmable apparatus on any suitable carrier medium. A tangible carrier medium may comprise a storage medium such as a hard disk drive, a magnetic tape device or a solid state memory device and the like. A transient carrier medium may include a signal such as an electrical signal, an electronic signal, an optical signal, an acoustic signal, a magnetic signal or an electromagnetic signal, e.g. a microwave or RF signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the present invention will become apparent to those skilled in the art upon examination of the drawings and detailed description. Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings.

Figure 1 illustrates a millimeter-wave communication system having two stations wishing to establish a directional multi-gigabit link between them using directional antenna;

Figure 2 illustrates some information exchanges in the millimeter-wave communication network of Figure 1 managed by a control or access point;

Figure 3 schematically illustrates a functional block diagram of a station implementing the invention;

Figure 4 illustrates a scenario of exchanges between two stations, implementing embodiments of the invention; and

Figure 5 is made of Figure 5a illustrating, using a flowchart, general steps at an initiating station in the scenario of Figure 4, and of Figure 5b illustrating, using a flowchart, general steps at a responding station in the same scenario of Figure 4.

DETAILED DESCRIPTION

Embodiments of the invention are now described by means of specific nonlimiting exemplary embodiments and by reference to the figures.

As briefly introduced above, Figure 1 illustrates a millimeter-wave communication system having two stations wishing to establish a directional link, such as a DMG link, between them using directional antennas.

If the two stations are more distant than a maximum range distance, for instance about tens of meters for 802.11ad, they are out of range of each other (102a).

With a distance between the two stations below the maximum range distance, various data rates can be achieved depending on said distance, each data rate available being associated with a Modulation and Coding Scheme (MCS). A first station 101, STA1, is a mobile wireless device equipped with an antenna array 111 which may be used in a directional mode or an omnidirectional mode. In use, STA1 can switch from one antenna pattern, numbered 1 to 8 for example, to another antenna pattern, and also switch to an omnidirectional antenna pattern. Each antenna pattern allows a directional sector to be selected in order to transmit or receive a signal over a 60GHz radio band.

Similarly, a second station 102, STA2, is a mobile wireless device equipped with an antenna array 112 which may be used in a directional mode or an omnidirectional mode. In use, STA2 can switch from one antenna pattern, numbered 1 to 8 for example, to another antenna pattern, and also switch to an omnidirectional antenna pattern. Each antenna pattern allows a directional sector to be selected in order to transmit or receive a signal over a 60GHz radio band.

As explained below, the omnidirectional antenna pattern is preferably used in an early processing to establish a 60GHz link between the two stations. The early processing is a sector sweep phase taking part of an antenna training (beamforming training in the standard), in order to discover the best antenna sector 1 to 8 for each of the stations.

The distance between the STA1 and STA2 is illustrated with the abscissa 120, between origin point 124 (having abscissa 0) corresponding to the position of STA2 along the line linking STA1 and STA2, and point 127 (having abscissa C) corresponding to the position of STA1 along the same line.

According to the distance C, the stations are able to determine a data rate 102b, 102c, 102d, 102e or 102f (or modulation and coding scheme named MCSO to MSC6 in the Figure) in order to exchange data with a satisfying packet error rate as defined in the IEEE 802.11 ad standard, for example lower than 1 %. A low data rate MCSO 102b is used for exchanging control information and for exchanging data in case the stations are very far one from the other (relatively to the maximum range distance).

The higher MCSs, from 102c to 102f, are used for high data rate data transfer between the two stations. The high data rate data transfers are known as Directional MultiGigabits DMG transfer in the standard, and shown in the Figure by reference 121.

The various MCSs cover a wide range of data rates from 27.5Mbps (MCSO 102b) to more than 2.5Gbps (MCS6 102f). The range of high data rates above MCS1 is huge over a short distance between origin point 124 and point 126 (of abscissa B, around ten meters). A data rate or MCS selection is implemented in the standard in order to select the most appropriate data rate given a traffic specification. Next, bandwidth may be allocated to the station wishing to transmit data, taking into account the data rate selected. The allocated bandwidth is usually defined as a time ratio or time period within a transmission opportunity. STA1 may be continuously moving relatively to STA2. For instance, the moving may be performed at a pedestrian speed when STA1 is a mobile telephone. Due to the moving, the data rate or MCS is continuously changing according to the relative distance C between the two stations.

As the selected data rate may decrease, the allocated time ratio of the transmission opportunity may become too small to allow all the data to be sent on time. It means that some applications in the stations, requiring very high data rate like high quality video streaming, can suffer from this instability of the data rates.

As an example, a video streaming of 600Mbps is only achievable with a minimum of MCS2 102d providing a data rate up to 770Mbps. A corresponding DMG coverage is shown in the Figure by reference 123, with an upper boundary 125 of abscissa A.

Data rates of MCSO 102b or MCS1 102c are too low to support this video streaming. A corresponding too low DMG coverage is shown in the Figure by reference 122. A DMG link originally established with one of data rates 102b or 102c or lately moving to one of data rates 102b or 102c thus becomes unusable for the current video streaming at 600Mbps. It results in a wasted bandwidth allocation for the overall 60GHz network.

Figure 2 illustrates some information exchanges in such millimeter-wave communication network managed by a control or access point 203. In the above-mentioned 802.11 ad standard, the millimetre-wave communication network is known as being a personal basic service set (PBSS), while a control point is known as being a PBSS Control Point, or PCP. The control or access point 203 acts as a coordinator to control (coordinate) access to the wireless medium by all the stations belonging to the PBSS. STA1 and STA2 can use an antenna sector sweep protocol described in the standard, to discover the antenna direction or sector to be used to transmit information to the other station.

For instance, an initiating station, for instance STA1, transmits (204), using successively each of its antenna sectors, an indication of a transmit sector sweep. The other and responding station, for instance STA2, is configured with an omnidirectional antenna pattern through which it receives the information from STA1. Responsive to the information, STA2 sends back (205) the best antenna sector to be used by STA1, i.e. the antenna sector of STA1 for which STA2 has detected the best reception quality. This best antenna sector will be used by STA1 to transmit control information to STA2 using low data rate of Common Mode Signaling ‘CMS’ modulation (MCSO 102b in Figure 1).

This procedure makes it possible for the two stations to establish a minimum information exchange using a low data rate mode. However, this low data rate mode is not applicable for high data rate which requires also defining the best antenna sector for the responding station, STA2.

The low data rate mode is set up during one or more small time periods within an ATI (announcement transmission interval) 211, a CBAP (contention based access period) 213 and/or an SP (service period) shown in Figure 2b.

In use, the coordinator 203 broadcasts the overall schedule access periods 206 and 207 to all the stations belonging to its managed network, using a repetition packet mode over different antenna sector established by PCP 203 in order to reach all the stations.

The schedule access periods correspond to time or allocation periods that are reserved to requesting stations inside a beacon interval. The beacon interval is the time between two successive beacon frames sent by PCP 203 to announce and organise the millimetre-wave network. An exemplary and simplified beacon interval is shown in Figure 2b.

Two types of access periods are available for the stations: a CBAP or contention based access period for which the station must contend (using EDCA method for instance) for access to the wireless medium against the other stations; and a SP or service period which is a uses contention free access period, meaning that it is a time scheduled period reserved by coordinator 203 to a link between two specific stations (one having made the request). An SP offers quality of service.

At a time, STA1 needs to establish a new DMG link for a data transfer with STA2. Thus, STA1 sends an access period request 208 to PCP 203. Request 208 describes STATs needs for data transfer, including a data rate, a time or allocation period duration specified as a fraction or multiple of the beacon interval, and a type of access (CBAP or SP) requested during DTI 212 forming the data transfer interval within the beacon interval, as shown in Figure 2b. The data rate, the time or allocation period duration and the type of access may form a traffic specification TSPEC in the meaning of the invention.

Responsive to request 208, PCP 203 provides an answer (not shown) to STA1 to grant the requested time allocation. The response schedules a corresponding access period for the current beacon interval. The scheduled access period is updated and broadcasted to all the stations using BTI 210a using new messages 206 and 207.

Following this time period allocation, a time period is reserved for STA1.

Upon accessing the reserved time period (either a scheduled SP or a CBAP through contention), a link is established with STA2 and data transfer 209 may start with a directional data transmission 214a between STA1 and STA2.

Note that other stations can also request a time allocation for the same beacon interval, resulting in having other time periods (214b is an example) used by the other stations.

Figure 2b shows an exemplary and simplified beacon interval, and identifies different time periods used to exchange different information between the stations and coordinator 203 in order to achieve the establishment of a data link.

The super frame shown in the Figure divides medium time in the PBSS, and is named beacon interval (Bl) in the standard. Subdivisions within the beacon interval are called access periods. Different access periods within a beacon interval have different access rules. The access periods are described in a schedule that is communicated by coordinator 203. The schedule communicated by coordinator 203 can include the following access periods: a beacon transmission interval (BTI) 210a during which one or more beacon frames are transmitted, an association beamforming training (A-BFT) 210 during which beamforming training is performed with each station that transmitted a beacon frame during BTI 210a, an announcement transmission interval (ATI) 211 during which a request-response based management access period is performed between coordinator 203 and stations, and a data transfer interval (DTI) 212 during which frame exchanges are performed between the stations. There is a single DTI per each beacon interval.

During DTI 212, a link is thus established between two stations allowing a data transfer to occur without involving any data transfer over coordinator 203. The link is established and maintained using the DMG protocol. During a CBAP or SP period, the DMG protocol makes it possible to adjust the antenna directions (or sectors) and optionally to support beam forming and beam tracking for the transmitter and the receiver, as the stations moves relatively one to each other.

Figure 3 schematically illustrates a functional block diagram of a station, either STA1 or STA2 or PCP 203, according to embodiments of the invention. The station is a communication device 300 adapted to communicate over a millimetre-wave communication network, such as an 802.11 ad network.

Communication device 300 can either be either of a transmitting device, a receiving device or both, and comprises: a Random Access Memory (RAM) 303, whose capacity can be extended by an additional Random Access Memory connected to an expansion port (not shown in the Figure); a Read-Only Memory (ROM) 302; a micro-controller or Control Process Unit (CPU) 301; a wireless communication interface 308, configured to perform communications with the other wireless communication devices of the network, a link layer controller (LLC) 304; and a presentation layer controller (PAL) 305. CPU 301, RAM 303, ROM 302 and the wireless communication interface 308 exchange data and control information via a communication bus 310.

In operation, after communication device 300 has been powered on, CPU 301 executes, from RAM 303, instructions forming a computer program, once these instructions have been loaded from ROM 302 or from an external memory (not shown in the Figure). The computer program causes CPU 301 to perform some or all of the steps of the algorithms described hereinafter in relation to Figures 4 to 6.

When controlling the overall operation of communication device 300, CPU 301 acts as a data analyzer unit, which analyses useful data payload (also referred as to MAC payload) of a packet received from another communication device, once processed by the wireless communication interface 308.

The wireless communication interface 308 comprises a Physical layer module (PHY) 307, a medium access controller (MAC) 306, and an antenna or antenna array 330.

As far as transmitting features of communication device 300 are concerned, PHY 307 is in charge of processing a signal output by MAC 306 from upper layers, before transmitting it over the wireless medium using antenna 330. For example, PHY 307 may perform modulation, frequency transposition and power amplification of a signal received from MAC 306.

Conversely, as far as receiving features of communication device 300 are concerned, PHY 307 is also in charge of processing a signal received by antenna 330, before providing it to MAC 306. The receiving process of PHY 307 may for instance include power amplification, frequency transposition and demodulation. MAC 306 manages the accesses, by communication device 300, to the wireless medium, according to access schemes (for instance schedule SP or contention for CBAP). MAC 306 also acts as a synchronization control unit, which controls synchronization relatively to each beacon interval shown in Figure 2b that schedules the transmissions via the millimetre-wave network. To do so, MAC 306 schedules the beginning and the end of an emission of data in the wireless network by antenna 330, as well as the beginning and the end of a reception of data from the wireless network by antenna 330.

Antenna 330 provides omnidirectional mode and directional modes making it possible to support directional MultiGigabits data transfer. Directional modes are obtained by selecting different antenna sectors for transmitting and receiving signals, through for instance a sector sweep procedure. Additionally, the wireless communication interface 308 is may be configured to perform antenna beam refinement and beam tracking as defined in the 802.11ad standard.

Communication device 300 acquires and renders application over interface 320 connected to an application. For instance, the application can be a compressed video stream, file storage, a video camera output or a display input. PAL 305 is a presentation layer controller converting application data into packets to be transmitted over the wireless network by communication interface 308. PAL 305 thus packetizes application data received from an application (for instance through interface 320) and transmits the packetized data to LLC 304. Conversely, in receiving mode, PAL 305 converts packets received from LLC 304 into data application to be input to interface 320.

The link layer controller LLC 304 is in charge of establishing a link, in particular DMG links in the case of 802.11ad networks, with other stations, in order to transmit and/or receive data packets at PAL and MAC layers. To perform the link establishment and manage the established link, LLC 304 exchange some control information with another station.

The present invention aims at reducing, even avoiding, situations in which a directional link, e.g. a DMG link according to 802.11 ad, becomes unusable, in particular as soon as it is established. This is because such uselessness is a waste of bandwidth for the whole millimetre-wave communication network.

An appropriate management of the DMG links, in particular during their establishment is proposed. This is why the present invention is preferably implemented in LLC 304.

To achieve that, the present invention first relies on conventional antenna training, e.g. beamforming training, between two stations, namely an initiating station and with a responding station.

Based on a result of the antenna training, for instance a metric value of an antenna signal reception quality, such as one of a signal-to-noise ratio, SNR, level and a received channel power indicator, RCPI, a first traffic specification defining traffic characteristics for a directional (e.g. DMG) link can be determined by the initiating station. The traffic specification includes for instance a data rate defining a data rate requirement given data to be transmitted and includes a time allocation defining a bandwidth requirement which may be determined based on the detected RCPI given the required data rate. Usually, a traffic specification as standardized in 802.11ad includes the type of access (schedule or contention-based) desired by the initiating station in addition to the time allocation. In other words, a traffic specification in the meaning of the invention may include a standardized traffic specification together with the required data rate.

Contrary to the conventional approach in which the first traffic specification is sent to the coordinator 203, the present invention provides that the determined first traffic specification is sent from the initiating station to the responding station, and responsive to the sending, a second traffic specification, preferably different from the first traffic specification, is received by the initiating station from the responding station. In particular, the responding station determines the second traffic specification defining traffic characteristics for a directional link based on the first traffic specification received.

This exchange of traffic specification contributes to a link negotiation between the two stations.

Next, the second traffic specification is used by the initiating station to perform, with the control or access point, a bandwidth allocation of a directional (DMG) link.

Thanks to the link negotiation, the directional link is also established based on link quality needs for the responding station. Thus there is less risks that the established directional link becomes useless due to incompatibility with responding station’s needs.

Specific embodiments seek to avoid establishing such a directional link in case conditions of link cannot be achieved. In such embodiments, the responding station may determine a link quality threshold as a condition to be reached by the directional link for the initiating station to trigger the bandwidth allocation with the control or access point, and then to send it to the initiating station together with the second traffic specification.

It results that no directional link is systematically established, but only when a sufficient link quality can be achieved, thereby avoiding wasting bandwidth.

Figure 4 illustrates a scenario of exchanges between STA1, STA2 and PCP 203, implementing embodiments of the invention. Figure 5a illustrates, using a flowchart, corresponding processing steps at the initiating station, i.e. STA1 in the example, while Figure 5b illustrates, using a flowchart, corresponding processing steps at the responding station, i.e. STA2 in the example. The arrows between Figure 5a and Figure 5b illustrate the exchange of information between the initiating station and the responding station.

The processes start with the antenna training, in particular a sector sweep phase, involving STA1 (step 501) and STA2 (step 551), as defined in 802.11 ad standard. During the exchanges of sector sweep, STA1 and STA2 discover their respective best sectors for transmitting using CMS (MCSO 102b - i.e. low data rate) to the other station which is configured with an omnidirectional for receiving.

As illustrated in Figure 4, STA1 first transmits data packets 405 to STA2 using different antenna sectors 404. Each data packet is transmitted with a value indicating the antenna sector used for transmission. At the same time, STA2 monitors all the transmissions with an omnidirectional antenna 406, and determines which best antenna sector BAS1 provides the better signal quality for STA1, in particular the highest received power level, RCPI1. This is step 552 of Figure 5b. In variant to RCPI, signal-to-noise ratio, SNR, can be used.

At the end of the transmissions by STA1, STA2 proceeds in the same manner by transmitting data packets 410 to STA1 using different antenna sectors 409. Each data packet is transmitted with a value indicating the antenna sector used for transmission, as well as with the best antenna sector BAS1 for STA1 and corresponding RCPI1 (408). It makes it possible for STA1 to obtain RCPI1 and BAS1 (step 502 of Figure 5a). At the same time, STA1 monitors all the transmissions with an omnidirectional antenna 407, and can determine which best antenna sector BAS2 provides the better signal quality for STA2, in particular the highest received power level, RCPI2.

At the end of the transmissions 410, STA1 sends a sector sweep feedback message to STA2 using its BAS1, to indicate the best antenna sector BAS2 for STA2 and the corresponding received power level RCPI2 (411).

After this sector sweep phase, both STA1 and STA2 are aware of their respective best antenna sectors and corresponding RCPI, thereby making it possible for them to exchange messages using an antenna sector for transmitting and using omnidirectional antenna for receiving.

In particular, during the next steps, STA1 transmits control information (in a message) to STA2 using the directional antenna configuration 408, i.e. using the determined antenna sector BAS1, while STA2 receives the information using an omnidirectional antenna configuration. Reciprocally, STA2 transmits control information to STA1 using the directional antenna configuration notified in the SSW feedback message 411, i.e. using the determined antenna sector BAS2, while STA1 receives the information using an omnidirectional antenna configuration.

Using RCPI1 received during sector sweep phase, STA1 can determine a first traffic specification defining traffic characteristics for a directional link. This is step 503 to determine an achievable modulation scheme together with an associated period allocation needed in order to satisfy the data rate of a feeding application.

To do so, STA1 determines an achievable MCS satisfying a packet error rate required (typically 1%) given a data rate (DATA_RATE) required by the application and considering usage of an additional gain provided by the antenna (either from STATs antenna or STA2’s antenna). For example, an additional gain (Antenna_Gain) of 12dB provided by the antenna gain can be typically considered.

It means that STA1 seeks for an achievable MCS associated with an RCPI above RCPI1 + Antenna_Gain.

In 802.11 ad standard, table 21-3 provides associations between RCPIs and MCSs as follows: RCPI_MCS0 = -78 dBm RCPI_MCS1 = -68 dBm RCPI_MCS2 = -66 dBm RCPI_MCS3 = -65 dBm RCPI_MCS4 = -64 dBm RCPI_MCS5 = -62 dBm RCPI_MCS6 = -63 dBm

Examples of data rate for each MCSx are provided in Figure 1.

Let assume MCSx be a determined scheme respecting RCPI_MCSx > RCPI1 + Antenna_Gain.

Next, STA1 determines a required bandwidth in term or time period ratio or percentage of the beacon interval: TIME_PERIOD = DATA_RATE / Data_Rate_MCSx;

The determined TIME_PERIOD and a type of access (SP or CBAP) desired by STA1 form the so-called standardized traffic specification (according to 802.11 ad). With addition of the DATA_RATE, they all form the first traffic specification TSPEC1.

Specific to the invention, a link negotiation is then engaged through exchanges 413 and 415. It corresponds to steps 504 and 505 at the initiating station and steps 553 to 556 at the responding station.

First, using a ‘Link request’ message 413, STA1 transmits the TSPEC1 information to STA2 at step 504. It is received by STA2 at step 553. This sharply contrasts to the 802.11 ad standard according to which the standardized traffic specification (TIME_PERIOD and type of access) in TSPEC1 should be sent directly to coordinator 203.

To do so, STA1 uses a directional mode of its antenna determined during the antenna training (i.e. BAS1) and STA2 uses an omnidirectional mode of its antenna for receiving TSPEC1. It means that transmission of TSPEC1 is made at low rate (using CMS).

Note that embodiments may perform steps 411 and 413 using one and the same message.

Based on received TSPEC1, STA2 estimates conditions for establishing a link with STA1 (step 414). This includes determining (step 554), based on TSPEC1, a second traffic specification TSPEC2 defining traffic characteristics for a directional link, and determining (step 555) at least one conditional parameter, for instance a link quality threshold, RCPIt, to be used by the initiating station as a condition to be reached by the directional link for the initiating station to trigger the bandwidth allocation with the control or access point.

One approach when determining TSPEC2 is to modify TSPEC1 in one way only, in particular with increasing of required data rate DATA_RATE or of required bandwidth or time period TIME_PERIOD. This is to ensure the original data stream to still be transmitted over any DMG link that could be established based on TSPEC2. For instance, the second traffic specification TSPEC2 may include an adjusted increased data rate compared to a data rate defined in the first traffic specification TSPEC1, and/or an adjusted increased time allocation compared to a time allocation defined in the first traffic specification. Thus, TSPEC2 would only include a data rate which is equal or greater than the one of TSPEC1 and/or a time period duration inside BTI which is also increased compared to TSPEC1.

The type of access (SP or CBAP) may remain unmodified in TSPEC2.

For illustrative purposes, one or more of the following rules may be implemented to determine TSPEC2: if the data traffic expected between STA1 and STA2 will generate a duplex traffic between the stations (like wireless remote processing), the data rate for TSPEC2 could be set to twice the data rate of TSPEC1; if the data traffic expected between STA1 and STA2 should be wirelessly relayed by STA2 to another station, the time period for TSPEC2 could be increased, if necessary, to permit STA2 to also reserve a time period to relay data received from STA1 to a third station using the same data rate as the one of TSPEC1; Also, if multicopies of the data of the traffic are required, the time period for TSPEC2 could be increased to support multi-copies; if STA2 is limited to track STA1 in mobility, the time period for TSPEC2 could be set to a multiple of the time period of TSPEC1, or simply increased given a mobility margin, to establish a data transmission with a more robust modulation and coding scheme (MCS).

For example, considering a first traffic specification TSPEC1 defined with a data rate of 100Mbps (throughput on medium with 1% of packet error rate) and with a time allocation of 20% of the beacon interval, it is determined, using Figure 1 for instance, that TSPEC1 can be operated using one or more MCS, in particular MCS2 102d providing a data rate of 770Mbps.

Indeed, the specified data rate of 100 Mbps can be achieved with a minimum of time allocation of 13% when using MCS2 (since 100/770 = 13%). This complies with the time allocation set in TSPEC1.

In case a relative mobility of STA1 and STA2 is detected while the link establishment is ongoing, the conditions set estimation 414 estimates an additional margin of one MCS range in order to ensure the link quality.

It means that, for the current example, TSPEC2 should comply with MCS1 102c (385Mbps) which is one-MCS degraded compared to MCS2 of TSPEC1. It results that the time allocation required becomes 26% (100/385) to support the data rate of 100Mbps.

Thus, STA2 sets TSPEC2 as follows: data rate for TSPEC2 = 100Mbps time allocation for TSPEC2 = 26%.

In any case, TSPEC2 as determined by STA2 can be operated with a corresponding MCSy that may be different from MCSx of TSPEC1.

Once TSPEC2 has been determined (step 554), conditional parameters may be also determined at step 554.

For instance, STA2 may be an RCPI threshold required to establish a link based on TSPEC2.

According to the determined MCSy for TSPEC2, a minimum RCPI threshold is computed based on an antenna gain, RX_ANT_GAIN_STA2, of STA2 (usually in directional and receiving mode along the best sector determined in the beamforming training) and/or on a mobility gain margin, MOB_GAIN (for example 6dB) to compensate mobility of the stations that creates impairment in the antenna beam adjustment.

In embodiments, the link quality threshold RCPIt is determined using the following formula:

RCPIt = RCPI_MCSy- RX_ANT_GAI N_STA2 + MOB_GAIN where RCPI_MCSy is a signal quality metric associated with MCSy (see for instance table 21-3 of 802.11ad standard reproduced above).

One may note that while STA1 has performed an approximate estimation on the achievable MCS (i.e. of TSPEC1) due to the fact that it performed the estimation based on typical value (for example using minimum receiver sensitivity level as defined in table 21-3 of the standard and on a typical antenna gain of 12dB), STA2, on its end, can perform a more precise estimation taking benefit of its knowledge of its own characteristics including its directional antenna gain and its receiver sensitivity according to each MCS.

That is why both TSPEC2 and RCPIt threshold are more efficient to drive the establishment of a DMG link between STA1 and ST2, compared to the sole TSPEC1.

The characteristics proper to each device 300 can be stored in ROM 302 of the device during a radio calibration process performed while manufacturing or testing it. If unknown while performing step 414, those characteristics can be the ones defined previously (receiver sensitivity level as defined in standard table 21-3 and a typical antenna gain of 12dB).

Next to step 414, determined TSPEC2 together with determined conditional (and triggering) parameters (for instance RCPIt) can be transmitted by STA2 to STA 1, using a ‘Link response’ message 415. This is step 556.

To do so, STA2 uses a directional mode of its antenna determined during the antenna training (i.e. BAS2) and STA1 uses an omnidirectional mode of its antenna for receiving TSPEC2 and RCPIt. It means that transmission of TSPEC2 is made at low rate (using CMS).

Thus, STA1 receives (step 505) a new traffic specification TSPEC2 replacing its initial TSPEC1, and a condition set CONDset of conditional parameters (including for instance RCPIt) to be used as triggering conditions to establish a DMG link defined by TSPEC2.

Following the link negotiation steps using ‘Link request’ and ‘Link response’ messages, STA1 and STA2 may continuously move and new sector sweep phases 416 and 417 can performed as described previously.

According to the mobility and the environment change and following each sector sweep phase, the measured received power levels RCPIs may vary, thus resulting in a varying TSPEC1, TSPEC2 and RCPIt. STA1 thus determines whether or not the conditions defined in CONDset are satisfied, during step 506 (also 418 in Figure 4).

This may for instance consist in checking whether or not the minimum measured received power RCPIS for STA2 during a sector sweep phase with STA1 is above RCPIt. Indeed, during the sector sweep phase, STA2 sends to STA1 the level of received power for the best antenna sector.

In other words, the obtained reception quality based on which the condition check is made is a received power level RCPI2 of the responding station as received by the initiating station from the responding station during the sector sweep phase.

If the conditions are not met, the process goes on with new antenna sector sweeps (loop back to step 501 in Figure 5a) without a DMG link being established. It means that it no sufficient signal quality is detected by STA1, given mobility margin added by STA2, no link is established, thus avoiding waste of bandwidth.

If the conditions are met, a DMG link can be established based on TSPEC2, and more particularly on the 802.11 ad-standardized traffic specification within TSPEC2. Thus, STA1 requests coordinator 203 for a time period allocation using TSPEC2 in order to establish the link.

To do so, STA1 sends (step 507) request 420 to add all or part of the traffic specification TSPEC2 involving STA2 to the network schedule. Responsive to the request, coordinator 203 allocates (step 421) a corresponding time period in DTI 212 (for example SP 214a in Figure 2b) and delivers an answer 422 to the request. In addition, coordinator 203 broadcasts, to all the stations including STA2, the corresponding (and thus updated) time schedule access over BTI 210a or ATI 211 using messages 423 and 424. This makes it possible for STA2 to know (step 557) that a data transfer will occur with STA1 or that a new antenna sector sweep is to be performed (loop back to step 551 in Figure 5b).

Once the broadcast time schedule informs of the TSPEC2-based time allocation for data traffic between STA1 and STA2, the two stations can perform a conventional beam refinement protocol 427 during the SP 214a following BTI 210a. STATs antenna and STA2’s antenna are trained (425 and 426) and a beam refinement is determined to obtain antenna configurations of the two stations enabling a high data rate (DMG) link.

As the conditions of this link establishment are the ones determined to reach the link quality (extrapolated during step 554), a DMG link 430 is thus established with the expected data rate taking into account both stations’ traffic (STA1 and STA2 ) and the expected link quality dealing with station mobility.

Once the DMG link is established and the requested period access is reached (either SP or through contention for CBAP), the allocated bandwidth of the DMG link is used to exchange data between STA1 and STA2 (steps 508 and 558).

Although the present invention has been described hereinabove with reference to specific embodiments, the present invention is not limited to the specific embodiments, and modifications will be apparent to a skilled person in the art which lie within the scope of the present invention.

Many further modifications and variations will suggest themselves to those versed in the art upon making reference to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the invention, that being determined solely by the appended claims. In particular the different features from different embodiments may be interchanged, where appropriate.

In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used.

Claims (26)

1. A method performed by an initiating station having an antenna operating in a millimeter-wave communication network managed by a control or access point, comprising the following steps: performing an antenna training with a responding station and determining, based on a result of the antenna training, a first traffic specification defining traffic characteristics for a directional link; sending the determined first traffic specification to the responding station, and responsive to the sending, receiving a second traffic specification from the responding station; and performing, with the control or access point, a bandwidth allocation of a directional link, using the second traffic specification.

2. A method performed by a responding station having an antenna operating in a millimeter-wave communication network managed by a control or access point, comprising the following steps: performing an antenna training with an initiating station, and subsequent to the antenna training, receiving a first traffic specification from the initiating station; determining, based on the first traffic specification, a second traffic specification defining traffic characteristics for a directional link; sending the determined second traffic specification to the initiating station for the latter to perform, with the control or access point, a bandwidth allocation of a directional link, using the second traffic specification.

3. The method of Claim 1 or 2, wherein the second traffic specification is sent or received from the responding station together with a link quality threshold as a condition to be reached by the directional link for the initiating station to trigger the bandwidth allocation with the control or access point.

4. The method of Claim 3, wherein the link quality threshold is based on an antenna gain, RX_ANT_GAIN_STA2, of the responding station and on a mobility gain margin, MOB_GAIN.

5. The method of Claim 4, wherein the link quality threshold RCPIt is determined using the following formula RCPIt = RCPI_MCSy- RX_ANT_GAI N_STA2 + MOBJ3AIN, where RCPI_MCSy is a signal quality metric associated with a modulation and coding scheme, MCSy, determined by the responding station from the second traffic specification.

6. The method of Claim 3 when depending on Claim 1, further comprising determining whether or not a reception quality obtained by the initiating station during a sector sweep phase with the responding station after the second traffic specification is received satisfies the link quality threshold, and only in case of positive determining, performing the bandwidth allocation step with the control or access point.

7. The method of Claim 6, wherein the obtained reception quality includes a received power level of the responding station as received by the initiating station from the responding station during the sector sweep phase.

8. The method of Claim 3 when depending on Claim 1, further comprising determining whether or not a directional link complying with the second traffic specification satisfies the link quality threshold, and only in case of positive determining, performing the bandwidth allocation step with the control or access point.

9. The method of Claim 6 or 8, wherein in case of negative determining, performing an antenna re-training.

10. The method of Claim 1, wherein the first traffic specification is sent using a directional mode of the antenna determined during the antenna training and the second traffic specification is received using an omnidirectional mode of the antenna.

11. The method of Claim 2, wherein the first traffic specification is received using an omnidirectional mode of the antenna, and the second traffic specification is sent using a directional mode of the antenna determined during the antenna training.

12. The method of Claim 1 or 2, wherein the second traffic specification is different from the first traffic specification.

13. The method of Claim 12, wherein the second traffic specification includes an adjusted increased data rate compared to a data rate defined in the first traffic specification, and/or an adjusted increased time allocation compared to a time allocation defined in the first traffic specification.

14. The method of Claim 12 when depending on Claim 2, wherein the adjusted increased data rate and/or the adjusted increased time allocation is or are determined by the responding station based on a maximum allowable bandwidth, a spare bandwidth to keep for one or more other stations, an overall bandwidth shared with one or more other stations, a mobility margin and/or a duplex or relay or multicopy requirement of data traffic between the two stations.

15. The method of Claim 1 or 2, wherein the antenna training comprises a sector sweep phase to discover a best antenna sector for each of the initiating station and the responding station.

16. The method of Claim 1 or 2 or 3, wherein the result of the antenna training and the link quality threshold, if any, include a metric value of an antenna signal reception quality.

17. The method of Claim 16, wherein the metric value is one of a signal-to-noise ratio, SNR, level and a received channel power indicator, RCPI.

18. The method of Claim 1 or 2, wherein the first and second traffic specifications include a data rate defining a data rate requirement and include a time allocation defining a bandwidth requirement.

19. The method of Claim 1, further comprising using the allocated bandwidth of the directional link to exchange data with the responding station.

20. The method of Claim 2, further comprising using the allocated bandwidth of the directional link to exchange data with the initiating station.

21. The method of Claim 1 or 2, wherein the millimeter-wave communication network operates over a 60Ghz band in accordance to IEEE 802.11ad standard.

22. An initiating station having an antenna operating in a millimeter-wave communication network managed by a control or access point, comprising: an antenna training module configured to perform an antenna training with a responding station; a traffic specification module configured to determine, based on a result of the antenna training, a first traffic specification defining traffic characteristics for a directional link; a communication interface configured to send the determined first traffic specification to the responding station, and responsive to the sending, to receive a second traffic specification from the responding station; and a bandwidth allocation module configured to perform, with the control or access point, a bandwidth allocation of a directional link, using the second traffic specification.

23. A responding station having an antenna operating in a millimeter-wave communication network managed by a control or access point, comprising: an antenna training module configured to perform an antenna training with an initiating station, a communication interface configured to receive, subsequently to the antenna training, a first traffic specification from the initiating station; a traffic specification module configured to determine, based on the first traffic specification, a second traffic specification defining traffic characteristics for a directional link; the communication interface being further configured to send the determined second traffic specification to the initiating station for the latter to perform, with the control or access point, a bandwidth allocation of a directional slink, using the second traffic specification.

24. A millimeter-wave communication system having a control or access point and at least two stations according to respectively an initiating station according to Claim 22 and a responding station according to Claim 23, establishing a directional multi-gigabit link between them.

25. A non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a station device of a millimeter-wave communication network, causes the station device to perform the method of Claim 1 or 2.

26. A method in a millimeter-wave communication network managed by a control or access point, substantially as herein described with reference to, and as shown in, Figure 4, or Figure 5a, or Figure 5b, or Figures 4, 5a and 5b of the accompanying drawings.