DESC:RELATED APPLICATION
Benefit is claimed to Indian Provisional Application No. 1815/CHE/2013 titled “METHOD AND SYSTEM OF ACQUIRING A MILLIMETER (MM) WAVE CARRIER IN A WIRELESS COMMUNICATION NETWORK " filed on 25th April 2013, which is herein incorporated in its entirety by reference for all purposes.

FIELD OF THE INVENTION

The present invention relates to the field of wireless communication systems, and more particularly relates to method and system for acquiring high frequency carrier in a wireless communication network.

BACKGROUND OF THE INVENTION

In the recent years several broadband wireless technologies have been developed to meet the growing number of broadband subscribers and to provide more and better applications and services. The 3rd Generation Partnership Project 2 (3GPP2) developed Code Division Multiple Access 2000 (CDMA 2000), 1x Evolution Data Optimized (1x EVDO) and Ultra Mobile Broadband (UMB) systems. The 3rd Generation Partnership Project (3GPP) developed Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA) and Long Term Evolution (LTE) systems. The Institute of Electrical and Electronics Engineers developed Mobile Worldwide Interoperability for Microwave Access (WiMAX) systems. As more and more people become users of mobile communication systems and more and more services are provided over these systems, there is an increasing need for a mobile communication system with large capacity, high throughput, lower latency and better reliability.

Super Mobile Broadband (SMB) system based on millimetre waves i.e. radio waves with wavelength in the range of 1millimeter (mm) to 10 mm, which corresponds to a radio frequency of 30 Gigahertz (GHz) to 300 GHz, is a candidate for next generation mobile communication technology as vast amount of spectrum is available in mmWave band. An SMB network as introduced in paper titled ”An introduction to Millimetre-Wave Broadband Systems” authored by Zhouyue Pi and Farooq Khan consists of multiple SMB base stations (BSs) that cover a geographic area. In order to ensure good coverage, SMB base stations need to be deployed with higher density than macro-cellular base stations. In general, roughly the same site-to-site distance as microcell or Pico-cell deployment in an urban environment is recommended. The transmission and/or reception in an SMB system are based on narrow beams, which suppress the interference from neighbouring SMB base stations and extend the range of an SMB link. However due to high path loss, heavy shadowing and rain attenuation reliable transmission at higher frequencies is one of the key issues that need to be overcome in order to make the millimetre wave systems a practical reality.

The lower frequencies in cellular band having robust link characteristics can be utilized together with higher frequencies in mmWave band to overcome the reliability issues in the SMB systems. In an asymmetric multiband multicarrier SMB network wherein the mobile station (MS) communicates with the communication network using asymmetric multiband carriers comprising at least one low frequency carrier in cellular band and at least one high frequency carrier in the mmWave band. The primary carrier i.e. carrier operating on low frequencies and the secondary/ extended carrier i.e. carrier operating on high frequencies may be transmitted by the same base station as illustrated in Figure 1. The base station broadcasts necessary information for identifying, acquiring and registering with the base station on the low frequency carrier. The high frequency with large bandwidth is used primarily for providing the high data rates services to the mobile users. Since the coverage of low frequency carrier and high frequency carrier is quite different the MS has to search and acquire the high frequency carrier even if the MS has acquired the low frequency carrier and has registered with the base station.

In a standalone system, the BS communicates with MS using only high frequency carrier. At higher frequency, the propagation path loss is higher and hence propagation distance is shorter. Beamforming techniques are used to decrease the propagation path loss and to increase the propagation distance for communication at higher frequency. Beamforming can be classified into Transmission (TX) beamforming performed in a transmitting end and reception (RX) beamforming performed in a receiving end. In general, the TX beamforming increases directivity by allowing an area in which propagation reaches to be densely located in a specific direction by using a plurality of antennas. In this situation, aggregation of the plurality of antennas can be referred to as an antenna array, and each antenna included in the array can be referred to as an array element.

The antenna array can be configured in various forms such as a linear array, a planar array, etc. The use of the TX beamforming results in the increase in the directivity of a signal, thereby increasing a propagation distance. Further, since the signal is almost not transmitted in a direction other than a directivity direction, a signal interference acting on another receiving end is significantly decreased. The receiving end can perform beamforming on a RX signal by using a RX antenna array. The RX beamforming increases the RX signal strength transmitted in a specific direction by allowing propagation to be concentrated in a specific direction, and excludes a signal transmitted in a direction other than the specific direction from the RX signal, thereby providing an effect of blocking an interference signal.

The BS transmits a synchronization signal through a Synchronization Channel (SCH) which assists MS to detect the presence of base station (BS). The BS also transmits the broadcast signal through a Broadcast Channel (BCH). The BCH carries essential system information which enables MS to have initial communication with the BS. The SCH & BCH are transmitted repetitively by performing beamforming on the channels with different transmission beams wherein each TX beam transmits the SCH and BCH in different direction. Because of hardware limitation (one antenna array is needed for one beam direction) the TX beams in different directions are transmitted at different times. The MS uses receive beamforming to detect the synchronization signal. MS uses multiple RX beams to detect the SCH transmission using multiple TX beams. Consider for example, SCH & BCH is transmitted using 4 TX beams and MS uses 4 RX beams to search the SCH & BCH. 4 TX beams are transmitted in four different time durations (e.g. slots) in a sub frame on the high frequency carrier as illustrated in Figure 1.

The MS first configures the receiver antenna array to receive using first Rx beam Rx1. The MS receives and searches for SCH for one sub frame duration using first Rx beam Rx1 as illustrated in Figure 2(A). The MS then configures the receiver antenna array to receive using second Rx beam Rx2 as illustrated in Figure 2(B). The MS receives and searches for SCH for one sub frame duration using second Rx beam Rx2. The same procedure is repeated for Rx beam 3 and Rx beam 4 as illustrated in Figure 2 (C) and Figure 2(D). Based on the reception in four sub frames MS determines the best TX and RX beam pair. During the initial acquisition of high frequency carrier MS is not synchronized with the transmissions of the base station and hence has to continuously process the received signals to detect the SCH. The MS also has to determine the TX beam ID in order to report the best TX beam to the BS. The TX beam ID may be indicated in the synchronization signal transmitted in SCH by scrambling the synchronizing signal with different scrambling code for different TX beams. This increases the processing effort by four times for MS as the MS has to descramble the received synchronization signal using four scrambling codes. Alternately the TX beam ID may be indicated as an information element in the system information carried in BCH or by using the different scrambling code for different TX beam transmitting the BCH. In this case after detecting the SCH MS has to receive the BCH to determine the TX beam ID. This method also increases the processing effort for MS as MS has to receive and decode the BCH.

In a system wherein the BS communicates with MS using low frequency carrier and high frequency carrier, the method of acquiring the high frequency carrier as used in standalone system is inefficient as explained above.

Therefore, there is a need of method and system for acquiring high frequency carrier in a wireless communication network in order to overcome the limitation as discussed.

SUMMARY OF THE INVENTION

An objective of the invention is to provide a system and method for acquiring high frequency carrier in a communication network.

An embodiment of the present invention describes a method of acquiring high frequency carrier in a communication network.

The method comprises receiving second carrier acquisition information, wherein the acquisition information comprises at least one of information about one or more synchronization signal beams being transmitted in each sector of a base station (BS), time interval information of a second carrier in which the synchronization signal beams being transmitted by BS, synchronization signal beam information of the one or more synchronization signal beams being transmitted by the BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by the mobile station (MS) and information about the one or more time intervals to be monitored by the MS, wherein the second carrier acquisition information being received by MS from BS on a first carrier, determining the one or more synchronization signal beams for monitoring by MS amongst a plurality of synchronization signal beams transmitted on the second carrier, determining the time intervals by the MS during which the determined synchronization signal beams being transmitted on the second carrier, and monitoring the second carrier at the determined time intervals by the MS to search and acquire the synchronization signal transmitted on the second carrier.
Another embodiment of the present invention describes a method of acquiring high frequency carrier in a communication network. The method comprises transmitting by a base station (BS) second carrier acquisition information wherein the acquisition information comprises at least one of information about one or more synchronization signal beams being transmitted in each sector of BS, time interval information of a second carrier in which synchronization signal beams being transmitted by BS, synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by a mobile station (MS) and information about the one or more time intervals to be monitored by MS, wherein the second carrier acquisition information being transmitted by BS on a first carrier.

Yet another embodiment of the present invention describes a system for acquiring high frequency carrier in a communication network. The system comprises means for receiving second carrier acquisition information comprising at least one of information about one or more synchronization signal beams being transmitted in each sector of a base station (BS), time interval information of a second carrier in which the synchronization signal beams being transmitted by BS, synchronization signal beam information of the one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by the mobile station (MS) and information about the one or more time intervals to be monitored by MS, wherein the second carrier acquisition information being received by MS from BS on a first carrier, means for determining the one or more synchronization signal beams for monitoring by MS amongst a plurality of synchronization signal beams transmitted on the second carrier, means for determining the time intervals by MS during which the determined synchronization signal beams being transmitted on the second carrier, and means for monitoring the second carrier at the determined time intervals by MS to search and acquire the synchronization signal transmitted on the second carrier.

Further embodiment of the present invention describes a system for acquiring high frequency carrier in a communication network. The system comprises means for transmitting by a base station (BS) second carrier acquisition information comprising at least one of information about one or more synchronization signal beams being transmitted in each sector of BS, time interval information of a second carrier in which synchronization signal beams being transmitted by BS, synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by a mobile station (MS) and information about the one or more time intervals to be monitored by MS, wherein the second carrier acquisition information being transmitted by BS on a first carrier.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The aforementioned aspects and other features of the present invention will be explained in the following description, taken in conjunction with the accompanying drawings, wherein:

Figure 1 illustrates a schematic representation of an asymmetric multiband multicarrier system.

Figures 2A to 2D illustrate a schematic representation of Synchronization Channel (SCH)/ Broadcast Channel (BCH) transmission and reception using beam forming in a standalone high frequency carrier system.

Figure 3 illustrates a timing diagram depicting timing synchronization between a low frequency and a high frequency carrier in the asymmetric multiband multicarrier system, according to one embodiment.

Figure 4A illustrates a system 400 for acquiring high frequency carrier in a communication network according to one embodiment of the present invention.

Figure 4B illustrates a schematic representation depicting information transmitted by Base station (BS) to assist Mobile station (MS) for searching and acquiring a high frequency carrier, according to one embodiment.

Figure 5 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network, according to one embodiment.

Figure 6 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network when Base station (BS) broadcasts information associated with synchronization signal beams transmitted in each sector, according to one embodiment.

Figure 7 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network when Base station (BS) unicasts information associated with synchronization signal beams transmitted in each sector, according to one embodiment.

Figure 8 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network when Base station (BS) broadcasts information regarding synchronization signal beams transmitted in each sector, according to another embodiment.

Figure 9 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network when Base station (BS) unicasts information associated with synchronization signal beams transmitted in each sector, according to another embodiment.

Figure 10 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network when a BS broadcasts information regarding synchronization signal beams transmitted in each sector, according to yet another embodiment.

Figure 11 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network when a BS unicasts information associated with synchronization signal beams transmitted in each sector, according to yet another embodiment.

Figure 12 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network, according to further embodiment.

Figure 13 illustrates a flow diagram of an exemplary method of acquiring high frequency carrier in a communication network, according to further embodiment.

Figure 14 illustrates a flow diagram of an exemplary method of activating a high frequency carrier, according to one embodiment.

Figure 15 illustrates a flow diagram of an exemplary method of activating a high frequency carrier, according to another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments. The present invention can be modified in various forms. Thus, the embodiments of the present invention are only provided to explain more clearly the present invention to the ordinarily skilled in the art of the present invention. In the accompanying drawings, like reference numerals are used to indicate like components.

The specification may refer to “an”, “one” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The present invention provides a method and system of acquiring high frequency carrier (i.e. millimeter (mm) Wave carrier) in a wireless communication network in which a base station communicates with a mobile station in the wireless communication network using asymmetric multiband carriers including at least one low frequency carrier in a cellular band and at least one high frequency carrier in a mmWave band.

Figure 1 illustrates a schematic representation of an asymmetric multiband multicarrier system 100 according to an embodiment of the present invention. In an asymmetric multiband multicarrier SMB network where a mobile station (MS) 101 communicates with a wireless communication network using asymmetric multiband carriers comprises at least one low frequency carrier in cellular band and at least one high frequency carrier in the mmWave band, the primary carrier i.e. carrier operating on low frequencies and the secondary / extended carrier i.e. carrier operating on high frequencies are transmitted by the same base station (BS) 102. The base station 102 broadcasts necessary information for identifying, acquiring and registering with the base station 102 on the low frequency carrier. The high frequency with large bandwidth is used primarily for providing the high data rates services to the mobile users. Since the coverage of low frequency carrier and high frequency carrier is quite different the MS 101 has to search and acquire the high frequency carrier even if the MS 101 has acquired the low frequency carrier and has registered with the base station 102.

Timing synchronization between low frequency carrier and high frequency carrier: In one embodiment of the present invention the low frequency carrier (also referred as 4G carrier or first carrier in the disclosure) and high frequency carrier (also referred as 5G carrier or second carrier in the disclosure) are transmitted in a time synchronized manner. Consider for example the transmission on low frequency carrier is divided into fixed time intervals (or frames) wherein each time interval is of one millisecond. Each frame may carry multiple OFDM symbols in case of OFDM based transmission on low frequency carrier. The transmission on high frequency carrier is also divided into fixed time intervals (or frames) wherein each time interval is of one millisecond. The time intervals on low frequency carrier and high frequency carrier may be different in different embodiments or systems. Each frame on the high frequency carrier may be further divided into slots wherein each slot carries one or more OFDM symbols in case of OFDM based transmission on the high frequency carrier. In one embodiment of the present invention, the frames of low frequency carrier and high frequency carrier are time synchronized as illustrated in Figure 3 (A). In this embodiment, location of synchronization signal transmitted in a frame of High frequency carrier can be determined using the ‘offset’ value from the start of the frame. Alternately in another embodiment of the present invention, the OFDM symbol in the low frequency carrier is synchronized with the slots in the high frequency carrier as illustrated in Figure 3 (B). In this embodiment if the SCH occupies the entire slot the location of SCH is determined using the OFDM symbol duration. For example SCH transmitted in slot 2 of high frequency carrier is 2 OFDM symbols away from the start of frame in low frequency carrier. Alternately if SCH occupies few OFDM symbols in slot 2 then OFDM duration + offset can be used to determine the location of SCH as illustrated in Figure 3 (C).

In the present invention, the MS first acquires the low frequency carrier and then acquires the high frequency carrier as and when needed. Since the low frequency carrier and high frequency carrier are transmitted by the same BS, the BS can assist the MS which has acquired the low frequency carrier and is registered with the BS. The BS assists the MS to acquire the high frequency carrier or 5G carrier as follows:

Time intervals for synchronization signal transmission: In one embodiment of the present invention, the base station informs to MS about the time intervals in which the synchronization signal is transmitted on the high frequency carrier. The synchronization signal is transmitted using beamforming in multiple directions wherein one or more beams transmission is separated in time. The base station transmits this information to MS on the low frequency carrier. This information may be broadcasted or sent in unicast manner to MS. In an alternate embodiment of the present invention, the synchronization signal beam transmission time intervals on high frequency carrier may be fixed in the system. In this case BS does not inform to MS about the time intervals in which the synchronization signal beam is transmitted on the high frequency carrier. The BS may also inform to MS about the timing of synchronization signal beam transmission on high frequency carrier with respect to timing on low frequency carrier. The information about the time intervals for synchronization signal beam transmission reduces the time MS has to monitor the high frequency carrier.

Synchronization signal beam information: In one embodiment of the present invention the base station also informs the MS about the ID of the synchronization signal beam transmitted in each of the indicated time intervals. Multiple synchronization signal beams may be transmitted depending on TX beamforming capability of BS. In case the multiple synchronization signal beams are transmitted at same time the scrambling code or beam sequence used to distinguish the multiple beams is also informed to MS. The BS transmits this information to MS on the low frequency carrier. In an alternate embodiment of the present invention there may be a fixed mapping between the beam IDs and time intervals in which the synchronization signal beam is transmitted. For example if four synchronization signal beams are transmitted in slot 1, slot 2, slot 3 and slot4, the beam ID for synchronization signal beam in slot 1 is Beam ID1, the beam ID for synchronization signal beam in slot 2 is Beam ID2, the beam ID for synchronization signal beam in slot 3 is Beam ID3 and the beam ID for synchronization signal beam in slot 4 is Beam ID4. In another example if two synchronization signal beams are transmitted in slot 1 and two synchronization signal beams are transmitted in slot 2 then beams in slot 1 can have beam ID1 and beam ID2 while beams in slot 2 can have beam ID 3 and Beam ID 4. Scrambling codes or beam sequences can be used to distinguish between two beams and beam IDs in a slot. For example, scrambling code 1 or beam sequence 1 corresponds to Beam ID1 and scrambling code 2 or beam sequence 2 corresponds to Beam ID2. The information about the synchronization signal beam IDs eliminates the need for MS to read BCH information to determine the Beam ID. It also eliminates the need for MS to identify beam ID by descrambling the code used to transmit the synchronization signal beam.

Sector Specific Beam information: In one embodiment of the present invention, the BS can inform the MS about the beams to be searched by it amongst the plurality of synchronization signal beams transmitted by the BS. This information is transmitted by BS on the low frequency carrier. The information about the specific beams to be searched by MS amongst the plurality of synchronization signal beams is determined as follows: The coverage of low frequency carrier transmitted by the BS is divided into multiple sectors. Each of these sectors may have different cell IDs or may have same cell IDs. Each of the plurality of synchronization signal beams transmitted on high frequency carrier is mapped to one of these sectors. Consider for example there are six synchronization signal beams transmitted on the high frequency carrier. Synchronization signal beam 1 and beam 2 are transmitted in area covered by sector 1, Synchronization signal beam 3 and beam 4 are transmitted in area covered by sector 2 and Synchronization signal beam 5 and beam 6 are transmitted in area covered by sector 3.

– Sectors with different cell IDs: In this embodiment when the MS acquires the low frequency carrier and registers with the BS, both the BS and MS are aware of the sector to which the MS is attached. Since the MS is attached on a specific sector, MS can search only for the synchronization signal beams transmitted in the sector. In one embodiment the BS transmits (broadcasts or unicast) information about the sectors and beam IDs in each sector. MS then determines the synchronization signal beams it has to search. In an alternate embodiment of the present invention, BS may determine the synchronization signal beams the MS has to search based on the sector to which MS is attached. BS then informs the MS about the beams to be searched by it amongst the plurality of synchronization signal beams on low frequency carrier.

– Sectors with same cell IDs: In this embodiment, the BS determines sector location of MS based on the antenna from which BS receives MS transmissions on low frequency carrier. Each sector has different antenna for reception. In one embodiment of the present invention BS may determine the synchronization signal beams the MS has to search based on the determined sector location of the MS using the receive antenna. BS then informs the MS about the beams to be searched by it amongst the plurality of synchronization signal beams on low frequency carrier.

In one embodiment of the present invention in addition to synchronization signal beams of sector to which the MS is attached, some synchronization signal beams of neighboring sector may also be monitored by the MS. The BS will inform these on the low frequency carrier to MS.

In one embodiment, the term “low frequency carrier”, “first carrier”, and “4G carrier” are used interchangeably throughout the disclosure. In one embodiment, the term “high frequency carrier”, “second carrier”, and “5G carrier” are used interchangeably throughout the disclosure.

Figure 4A illustrates a block diagram of a system 400 for acquiring high frequency carrier in a communication network according to one embodiment of the present invention. The system 400 comprises at least one mobile station (MS) and at least one base station (BS). The at least one MS and the at least one BS are coupled to each other through a communication network 404. The MS includes, but not limited to, a low frequency transceiver (Tx/Rx) module 401, a high frequency receiver (Rx) module 402, and a high frequency acquisition module 403. The BS includes, but not limited to, a low frequency transceiver (Tx/Rx) module 405, and a high frequency transceiver (Tx/Rx) module 406.

Figure 4B illustrates an embodiment in which information being transmitted by BS assists the acquisition of high frequency carrier depending on how the synchronization signal is transmitted by BS. MS is in coverage of BS and is attached to Sector 1 of the BS. BS coverage is divided into three sectors. There are two methods followed by BS for transmitting the synchronization signal on high frequency carrier. In the first method, BS transmits all the beams of synchronization signal in one sub frame of high frequency carrier. Each beam is transmitted in different slot of sub frame. Same is repeated for other sub frames. In this method MS first configures the first RX beam RX1 and searches for synchronization signal beams in sub frame 1 and then it configures the second RX beam RX2 and searches for synchronization signal beams in sub frame 2. In order to assist the MS in searching the synchronization signal, BS provides one or more of the following information to MS:
a) SCH slots in SF: 0,2,4,6,8,10
b) Beam IDs in SCH slot: B2, B3, B4, B5, B0, B1
c) Current sector beam: B2, B3
d) Neighbouring beam of current sector: B4, B1

In the second method, BS transmits one synchronization signal beam in one sub frame. Multiple transmissions of same synchronization signal beam is done in one sub frame. In this method, MS uses both the RX beam RX1 and RX beam RX2 one after another in each sub frame to search for synchronization signal. In order to assist the MS in searching the synchronization signal, BS provides one or more of the following information to MS:
a) SCH slots in SF: 0, 2,4,6,8
b) Number of TX beams: 6
c) Beam ID in SF: SF1 (B2), SF2(B3), SF3(B4), SF4(B5), SF5(B0), SF6(B1); Starting SF number of group of 6 SFs is provided
d) Current sector beam: B2, B3
e) Neighbouring beam of current sector: B4, B1

Figure 5 illustrates a flow diagram of a method of searching and acquiring high frequency carrier in a communication network, according to one embodiment. MS receives a trigger from BS to search and acquire the synchronization signal transmitted on the high frequency carrier or MS may decide on its own to search and acquire the synchronization signal transmitted on the high frequency carrier. In step 501, MS receives the high frequency carrier acquisition information from BS on the low frequency carrier. The received high frequency carrier acquisition information comprising at least one of information about one or more synchronization signal beams being transmitted in each sector of BS, time interval information of high frequency carrier in which the synchronization signal beams being transmitted by BS, synchronization signal beam information of the one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by the MS and information about the one or more time intervals to be monitored by MS. The synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam. The high frequency carrier acquisition information may comprise information to acquire the high frequency carrier of BS to which MS is attached or to acquire the high frequency carrier of neighbour BS or both. The high frequency carrier acquisition information may be broadcasted by BS. Alternately the high frequency carrier acquisition information may be sent by BS in dedicated signalling.

In step 502, MS determines the synchronization signal beams it needs to monitor amongst the plurality of synchronization signal beam transmitted on high frequency carrier. In one embodiment MS may monitor all the synchronization signal beams transmitted by the BS. In alternate embodiment the MS may monitor some of the synchronization signal beams transmitted on high frequency carrier. MS determines the one or more synchronization signal beams corresponding to the sector on which the MS is attached with BS using the received high frequency carrier acquisition information comprising information about the one or more synchronization signal beams being transmitted in each sector of BS. In another embodiment MS monitors the synchronization signal beams indicated in the received second carrier acquisition information for MS monitoring. The received synchronization signal beams information for MS monitoring in the high frequency carrier acquisition information are determined by BS based on the sector to which MS is attached. .

In step 503, MS determines the time intervals on the high frequency carrier where the determined synchronization signal beams is transmitted. In one embodiment the time intervals of synchronisation signal beam transmission and mapping between time intervals and synchronisation signal beams is transmitted by BS in high frequency carrier acquisition information. The time intervals corresponding to the determined synchronization signal beams are determined using the received high frequency carrier acquisition information comprising of time interval information of the second carrier in which the synchronization signal beams being transmitted by BS and the synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of indicated time interval. In alternate embodiment the time intervals of synchronisation signal beam transmission are pre-defined and mapping between pre-defined time intervals and synchronisation signal beams is transmitted by BS in high frequency carrier acquisition information. The time intervals corresponding to the determined synchronization signal beams are determined using the received high frequency carrier acquisition information comprising of synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of predefined time interval for synchronization signal beam transmission on the second carrier. In yet another embodiment the time intervals of synchronisation signal beam transmission and mapping between time intervals and synchronisation signal beams are predefined. The time intervals corresponding to the determined synchronization signal beams are determined using the predefined time intervals for synchronization signal beam transmission and the predefined mapping between one or more synchronization signal beams and the time interval for synchronization signal beam transmission. In another embodiment MS monitors the time intervals indicated in the received second carrier acquisition information for MS monitoring. The received time interval information for MS monitoring in the high frequency carrier acquisition information are determined by BS based on the sector to which MS is attached.

In step 504, MS monitors the high frequency carrier at the determined time intervals to search and acquire the synchronization signal transmitted on the high frequency carrier.

In step 505, beam ID of the acquired synchronization signal beam is determined. The beam ID of the successfully received synchronization signal beam is determined based on at least one of the time intervals in which the synchronization signal beam is received and the beam sequence. The synchronization signal beam information comprising at least one of beam ID and beam sequence of the successfully received one or more synchronization signal beams may also be reported by the MS to BS on the low frequency carrier.

Figure 6 illustrates a flow diagram of a method of searching and acquiring a high frequency carrier according to one embodiment.

In this embodiment, MS acquires and registers with BS on a low frequency carrier at step 601. BS then broadcasts high frequency carrier acquisition information to MS on the acquired low frequency carrier at step 602. The information which is broadcasted includes, but not limited to, time interval information of the high frequency carrier in which synchronization signal beams being transmitted by BS, synchronization signal beam information of one or more synchronization signal beams being transmitted by the BS in each of indicated time interval, information about the one or more synchronization signal beams being transmitted in each sector of the BS The synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam.
Subsequently, BS sends a high frequency carrier search command to MS on the acquired low frequency carrier at step 603.

Figure 7 illustrates s a flow diagram of a method of searching and acquiring a high frequency carrier according to another embodiment of the present invention.

In one exemplary embodiment, MS acquires and registers with BS on a low frequency carrier at step 701. BS then unicasts a high frequency carrier search command to MS at step 702. The search command includes, but not limited to, time interval information of the high frequency carrier in which synchronization signal beams being transmitted by BS, synchronization signal beam information of one or more synchronization signal beams being transmitted by the BS in each of indicated time interval, information about the one or more synchronization signal beams being transmitted in each sector of the BS. The synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam.

In another exemplary embodiment, MS acquires and registers with BS on a low frequency carrier at step 701. MS then sends a high frequency carrier search request to BS at step 703. BS in return provides a high frequency carrier search response to MS at step 704. The search response includes, but not limited to, time interval information of the high frequency carrier in which synchronization signal beams being transmitted by BS, synchronization signal beam information of one or more synchronization signal beams being transmitted by the BS in each of indicated time interval, information about the one or more synchronization signal beams being transmitted in each sector of the BS. The synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam.

Figure 8 illustrates a flow diagram of a method of searching and acquiring a high frequency carrier in a communication network according to one embodiment in which the time slots used for synchronization signal beams are fixed in the communication network.

In one exemplary embodiment, MS acquires and registers with BS on the low frequency carrier at step 801. BS then broadcasts high frequency carrier acquisition information to MS on the acquired low frequency carrier at step 802. The information includes but not limited to, synchronization signal beam information of one or more synchronization signal beams being transmitted by the BS in the pre-defined time intervals for synchronization signal transmission, information about the one or more synchronization signal beams being transmitted in each sector of the BS. The synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam. Subsequently BS sends a high frequency carrier search command to MS on the acquired low frequency carrier at step 803.

Figure 9 illustrates a flow diagram of a method of searching and acquiring a high frequency carrier, according to another embodiment in which the time slots used for synchronization signal beams are fixed in the communication network.

In one exemplary embodiment, MS acquires and registers with BS on the low frequency carrier at step 901. BS then sends a high frequency carrier search command to MS on the acquired low frequency carrier at step 902. The search command includes but not limited to, synchronization signal beam information of one or more synchronization signal beams being transmitted by the BS in the pre defined time intervals for synchronization signal transmission, information about the one or more synchronization signal beams being transmitted in each sector of the BS. The synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam.

In another embodiment, MS acquires and registers with BS on the low frequency carrier at step 901. MS then sends a high frequency carrier search request to BS on the acquired low frequency carrier at step 903. Subsequently, BS provides a high frequency carrier search response to MS on the acquired low frequency carrier at step 904. The search response includes, but not limited to, synchronization signal beam information transmitted in each sector, and beam IDs of high frequency synchronization signal beams transmitted in each sector.

Figure 10 illustrates a flow diagram of a method of searching and acquiring a high frequency carrier according to one embodiment in which a fixed mapping is provided between the beam ID and the synchronization signal slots. In this embodiment, the time slots used for synchronization signal beams are also fixed in the communication network.

In one exemplary embodiment, MS acquires and registers with BS on the low frequency carrier at step 1001. BS then broadcasts high frequency carrier acquisition information to MS on the acquired low frequency carrier at step 1002. The information includes, but not limited to synchronization signal beam information transmitted in each sector.

In another exemplary embodiment, BS sends a high frequency carrier search command to MS on the acquired low frequency carrier at step 1003.

Figure 11 illustrates a flow diagram of a method of searching and acquiring a high frequency carrier according to another embodiment in which a fixed mapping is provided between the beam ID and the synchronization signal slots. In this embodiment, the time slots used for synchronization signal beams are also fixed in the communication network.

In one exemplary embodiment, MS acquires and registers with BS on the low frequency carrier at step 1101. BS then unicasts a high frequency carrier search command to MS on the acquired low frequency carrier at step 1102. The search command includes, but not limited to, synchronization signal beam information transmitted in each sector.

In another exemplary embodiment, MS acquires and registers with BS on the low frequency carrier at step 1101. MS then sends a high frequency carrier search request to BS on the acquired low frequency carrier at step 1103. Subsequently BS provides a high frequency carrier search response to MS on the acquired low frequency carrier at step 1104. The search response includes but not limited to, synchronization signal beam information transmitted in each sector.

Figure 12 illustrates a flow diagram of a method of searching and acquiring a high frequency carrier in a communication network, according to further another embodiment. In this embodiment, BS determines time slots of the high frequency carrier during which MS monitors the high frequency carrier for the synchronization signal beams. The time slots used for synchronization signal beams being fixed in the communication network. The beam IDs of synchronization signal beams is determined using the mapping between the time slot and beam ID. Here, the mapping is fixed mapping.

In one exemplary embodiment, MS acquires and registers with BS on low frequency carrier at step 1201. MS then sends a high frequency carrier search request at step 1202. Subsequently, BS determines synchronization signal beams corresponding to a sector to which MS being attached at step 1203. Later BS sends a high frequency carrier search response to MS at step 1204. Here, the high frequency carrier search response comprises synchronization signal beams to search and optionally beam ID, and time slot of high frequency carrier that MS needs to monitor for receiving synchronization signal beams.

Figure 13 illustrates a flow diagram of a method of searching and acquiring a high frequency carrier, according to further embodiment. In this embodiment, MS acquires and registers with BS on low frequency carrier at step 1301. BS then determines synchronization beams corresponding to the sector to which MS being attached at step 1302 and sends a high frequency carrier search command to MS at step 1303. The high frequency search command, includes but not limited to, synchronization signal beams to search, and time slot of high frequency carrier that MS needs to monitor for receiving synchronization signals.

Further, a high frequency carrier search result is provided from MS to BS in one more embodiments described above. The search result includes, but not limited to, carrier frequency, beam ID of synchronization signal beam received, beamforming capabilities etc.

Figure 14 illustrates triggering of the activation of high frequency carrier according to one embodiment. MS initiates connection and transmits connection request with QoS parameters for the requested connection. BS determines whether the QoS requested requires high frequency carrier (or 5G carrier) or not. BS also determines if the MS/BS supports 5G carrier capability or not. 5G carrier operation is complex and power consuming. 5G carriers should be activated only if QoS requested can only be met by 5G carrier. BS can be aware of MS’s 5G capability in one of the following ways: 1) MS can send this information during the registration. 2) MS can send this information along with connection request. If the BS/MS supports 5G capability and QoS requested requires 5G carrier then BS sends 5G carrier acquisition request message with information about 5G carrier parameters like carrier frequency, frequency band, beamforming parameters as explained earlier in the present invention. MS acquires the 5G carrier based on information received from BS and sends the 5G carrier acquisition response to MS. On receiving the 5G carrier acquisition response BS sends a connection response to MS. BS indicates if the connection request is accepted or not. If accepted it also indicates the QoS parameters depending on whether 5G carrier was acquired or not. If the requested QoS required 5G carrier and 5G carrier was not acquired by MS, BS can downgrade the QoS of connection or may reject the connection. The activation of 5G carrier when connection request is initiated by BS is illustrated in Figure 15.

Dynamic transmission of synchronization signal on high frequency carrier: In one embodiment of the present invention the BS always transmits the synchronization signal using beamforming. In an alternate embodiment of the present invention BS transmits the synchronization signal beam(s) in a sector based on MS location. If there is an MS attached to a sector of BS on the low frequency carrier then only BS transmits one or more synchronization signal beam of that sector. One or more synchronization signal beams in neighbouring sector of the sector to which the MS is attached on low frequency carrier may also be transmitted on high frequency carrier.

In one embodiment of the present invention, BS may dynamically decide the synchronization signal slots for the beams based on number of beams enabled for transmission BS may for e.g. Consider 4 synchronization signal beams are used on high frequency carrier. If all synchronization signal beams are switched on, beam 1, beam 2, beam 3 and Beam 4 are transmitted in slots T1, T2, T3 and T4 respectively (T1: B1, T2: B2, T3: B3, T4: B4). If beam 2 and beam 3 are switched off as there are no MS in those sectors, the transmission slot of beam 4 can be changed from slot T4 to T2 (T1: B1, T2: B4, T3: No Tx, T4: No Tx)

The methods explained in the present invention can also be used for searching high frequency carrier of not only the BS to which MS is attached but also of neighboring BS.

Although the invention of the method and system has been described in connection with the embodiments of the present invention illustrated in the accompanying drawings, it is not limited thereto. It will be apparent to those skilled in the art that various substitutions, modifications and changes may be made thereto without departing from the scope and spirit of the invention. ,CLAIMS:
1. A method of acquiring high frequency carrier in a communication network, the method comprising:
receiving second carrier acquisition information comprising at least one of information about one or more synchronization signal beams being transmitted in each sector of a base station (BS), time interval information of a second carrier in which the synchronization signal beams being transmitted by BS, synchronization signal beam information of the one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by the mobile station (MS) and information about the one or more time intervals to be monitored by MS, wherein the second carrier acquisition information being received by MS from BS on a first carrier;
determining the one or more synchronization signal beams for monitoring by MS amongst a plurality of synchronization signal beams transmitted on the second carrier;
determining the time intervals by MS during which the determined synchronization signal beams being transmitted on the second carrier; and
monitoring the second carrier at the determined time intervals by MS to search and acquire the synchronization signal transmitted on the second carrier.

2. The method as claimed in claim 1, wherein determining one or more synchronization signal beams for monitoring by MS amongst a plurality of synchronization signal beams transmitted on the second carrier comprises:
determining the one or more synchronization signal beams corresponding to the sector on which the MS is attached with BS using the received second carrier acquisition information,
wherein the acquisition information comprises information about the one or more synchronization signal beams being transmitted in each sector of BS in the received second carrier acquisition information.

3. The method as claimed in claim 1, wherein determining time intervals by MS during which the determined synchronization signal beams being transmitted on the second carrier comprises:
determining time intervals corresponding to the determined synchronization signal beams using the received second carrier acquisition information,
wherein the acquisition information comprises time interval information of the second carrier in which the synchronization signal beams being transmitted by BS and the synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of indicated time interval.

4. The method as claimed claim 1, wherein determining time intervals by MS during which the determined synchronization signal beams being transmitted on the second carrier comprises:
determining time intervals corresponding to the determined synchronization signal beams using the received second carrier acquisition information,
wherein the acquisition information comprises synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of predefined time interval for synchronization signal beam transmission on the second carrier.

5. The method as claimed in claim 1, wherein determining time intervals by MS during which the determined synchronization signal beams being transmitted on the second carrier comprises:
determining time intervals using the predefined time intervals for synchronization signal beam transmission and the predefined mapping between one or more synchronization signal beams and the time interval for synchronization signal beam transmission corresponding to the determined synchronization signal beams.

6. The method as claimed in claim 1, wherein the second carrier acquisition information received by MS on the first carrier is broadcasted by BS.

7. The method as claimed in claim 1, wherein the second carrier acquisition information received by MS on the first carrier is sent to MS by BS using dedicated signalling.

8. The method as claimed in claim 7, wherein the second carrier acquisition information received by MS on the first carrier is sent to MS in response to second carrier acquisition request sent by MS to BS.

9. The method as claimed in claim 7, wherein the second carrier acquisition information received by MS on the first carrier is sent to MS in response to connection request sent by MS to BS.

10. The method as claimed in claim 1, wherein the synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam.

11. The method as claimed in claim 1, further comprising: determining a beam ID of the successfully received synchronization signal beam, wherein the beam ID of successfully received synchronization signal beam is determined based on at least one of the time interval in which the synchronization signal beam is received and the beam sequence.

12. The method as claimed in claim 11, wherein the synchronization signal beam information comprising at least one of beam ID and beam sequence of the successfully received one or more synchronization signal beams reported by the MS to BS on the first carrier.

13. The method as claimed in claim 1, wherein the first carrier is a low frequency carrier and the second carrier is a high frequency carrier.

14. The method as claimed in claim 1, wherein the second carrier acquisition information comprises information to acquire the second carrier of BS to which MS is attached or to acquire the second carrier of neighbour BS.

15. The method as claimed in claim 1, wherein determining one or more synchronization signal beams for monitoring by MS amongst a plurality of synchronization signal beams transmitted on the second carrier further comprises
monitoring the synchronization signal beams indicated in the received second carrier acquisition information for MS monitoring.

16. The method as claimed in claim 15, wherein the received synchronization signal beams information for MS monitoring in the second carrier acquisition information are determined by BS based on the sector to which MS is attached.

17. The method as claimed in claim 1, wherein determining time intervals by MS during which the determined synchronization signal beams being transmitted on the second carrier further comprises:
monitoring the time intervals indicated in the received second carrier acquisition information for MS monitoring.

18. The method as claimed in claim 17, wherein the time interval information corresponds to synchronization signal beams for MS monitoring determined by BS based on the sector to which MS is attached.

19. A method of acquiring high frequency carrier in a communication network, the method comprising:
transmitting by a base station (BS) second carrier acquisition information comprising at least one of information about one or more synchronization signal beams being transmitted in each sector of BS, time interval information of a second carrier in which synchronization signal beams being transmitted by BS, synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by a mobile station (MS) and information about the one or more time intervals to be monitored by MS, wherein the second carrier acquisition information being transmitted by BS on a first carrier.

20. The method as claimed in claim 19, wherein the second carrier acquisition information is broadcasted by BS.

21. The method as claimed in claim 19, wherein the second carrier acquisition information is transmitted to MS using dedicated signalling.

22. The method as claimed in claim 21, wherein the second carrier acquisition information is transmitted to MS in response to a second carrier acquisition request received from MS.

23. The method as claimed in claim 21, wherein the second carrier acquisition information is transmitted to MS in response to a connection request received from MS.

24. The method as claimed in claim 19, wherein the synchronization signal beam information comprises at least one of a beam identifier and beam sequence corresponding to a beam.

25. The method as claimed in claim 19, wherein the first carrier is a low frequency carrier and the second carrier is a high frequency carrier.

26. The method as claimed in claim 19, wherein the second carrier acquisition information comprises information to acquire the second carrier of BS or to acquire the second carrier of neighbour BS.

27. The method as claimed claim 19, wherein the synchronization signal beams to be monitored by MS is determined based on a sector to which MS is attached with BS.

28. The method as claimed in claim 19, wherein the time intervals to be monitored by MS is determined based on a sector to which MS is attached with BS.

29. A system for acquiring high frequency carrier in a communication network, the system comprising:
means for receiving second carrier acquisition information comprising at least one of information about one or more synchronization signal beams being transmitted in each sector of a base station (BS), time interval information of a second carrier in which the synchronization signal beams being transmitted by BS, synchronization signal beam information of the one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by the mobile station (MS) and information about the one or more time intervals to be monitored by MS, wherein the second carrier acquisition information being received by MS from BS on a first carrier;
means for determining the one or more synchronization signal beams for monitoring by MS amongst a plurality of synchronization signal beams transmitted on the second carrier;
means for determining the time intervals by MS during which the determined synchronization signal beams being transmitted on the second carrier; and
means for monitoring the second carrier at the determined time intervals by MS to search and acquire the synchronization signal transmitted on the second carrier.

30. A system for acquiring high frequency carrier in a communication network, the system comprising:
means for transmitting by a base station (BS) second carrier acquisition information comprising at least one of information about one or more synchronization signal beams being transmitted in each sector of BS, time interval information of a second carrier in which synchronization signal beams being transmitted by BS, synchronization signal beam information of one or more synchronization signal beams being transmitted by BS in each of indicated time interval, information about the one or more synchronization signal beams to be monitored by a mobile station (MS) and information about the one or more time intervals to be monitored by MS, wherein the second carrier acquisition information being transmitted by BS on a first carrier.