Patent ID: 12237908

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In describing the preferred embodiments of the present disclosure illustrated in the drawings, specific terminology is resorted to for the sake of clarity. However, the present disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.

Turning to the drawings,FIG.1shows a high-powered large phased-array satellite system10that creates a large number of beams212covering small terrestrial cells232on the Field of View (FOV)230of a given satellite210. The system10includes a base station100that communicates with the satellite210. The base station100can have Base Transceivers such as eNodeBs140in 4G system, and a processor/core120(such as the Evolved Packet Core in 4G system) that communicates with the Internet110. The base Transceivers140communicates signals to a gateway150having an antenna such as a directional antenna that communicates with the satellite210via gateway link signals152. In one embodiment, the satellite210can be a single satellite device. In another embodiment, the satellite210can be a plurality of satellite antenna elements, such as disclosed in U.S. Pat. No. 9,973,266, the entire contents of which are hereby incorporated by reference.

The satellite210receives the gateway antenna signals152and retransmits them as signals to user terminals located in the satellite FOV230, which includes one or more cells232. The satellite signals include multi-beam user links which comprise nominal beams (NB)212, and wide beam (WB)214provided by the satellite phased array antenna.

Unmodified user devices connect to these beams212,214as they would to a local cell tower in a terrestrial system. The signals from/to the user devices are directed by the satellite system to/from the gateway150via high-throughput gateway links (such as Ka-band links, Q/V band links, or laser links). The total gateway link bandwidth is sufficient to accommodate the aggregated signals from all beams (cells) including traffic and network/access signals. At the gateway150, the user signals are digital and/or analog processed and interfaced with custom Base Transceivers such as eNodeBs140.

These customized eNodeBs140provide a standards-compliant interface to unmodified user devices, allowing them to connect as they would to a local tower while compensating for the effects (such as delay and Doppler shift) of the satellite communication system. The eNodeBs140are modified to tolerate large latency due to signal propagation to/from a satellite210. Delay and Doppler shift are compensated at each cell (beam) center so the differential delay and Doppler over a size limited cell will be small and within the standard UE capability.

Referring toFIGS.2-3as an example using narrow channel bandwidth for network broadcasting/accessing signals for all beams that do not carry traffic, a beam is shown carrying traffic to/from UE support channel bandwidth of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, and up to 4×10 MHz in the 3GPP bands. A beam without traffic has broadcast/access channel signals using only 1.4 MHz channel bandwidth for UE access and attachment to the network. There are ˜2800 nominal beamwidth beams generated by the satellite phased array antenna and each beam covers one of the ˜2800 uniform cells within the entire satellite Field of View (FOV). Gateway beam utilizes Q/V band in both orthogonal polarization (i.e. LHCP and RHCP) with total 9 GHz available bandwidth. The channel in each user beam (carrying traffic or carrying no-traffic) is mapped to a frequency slot in Q/V band gateway beam. Any increase of the channel bandwidth for the beams without traffics will impact the available bandwidth for the beams with traffics and therefore has negative impact to the total satellite capacity or the number of beams available to cover the ˜2800 cells in the satellite FOV resulting uncovered/unserved areas within FOV. Therefore, a more flexible approach that uses less bandwidth resource for the network broadcast/access beams while providing a complete coverage over the entire FOV is necessary.

FIG.4shows the satellite FOV230ofFIG.1, having a plurality of cells232. Here, the cells are completely illuminated by a set of Wide Beams (WBs)214. The beamwidth of each wide beam (WB)214can be controlled to cover a cluster of adjacent cells. Each nominal beam (NB)212a,212bcan be controlled to communicate with a single cell232. The FOV230can have a plurality of WB214a,214b, each one covering a plurality of cells232or portions of cells232. The WBs214a,214bcan overlap slightly and some cells232may partially or wholly be covered by more than one WB214a,214b.

As further shown inFIG.4, the FOV230includes active cells (ACs) and inactive cells (IACs). An active cell (AC) is a cell with connected UE(s) and real traffic. The number of ACs is represented as NAC. An active beam (AB)212ais a nominal beam tracking a given AC with signal channel bandwidth of BWAC. The number of ABs is represented as NAB(NAB=NAC). An inactive cell (IAC) is a cell without connected UE(s) and traffic except the network access information/communications. The number of IACs is represented as NIC. An inactive beam (IAB)212bis a nominal beam which covers an IAC with signal channel bandwidth of BWIC. The number of IABs, each covers an IAC, is represented as NiBC. The number of wide beams (WBs), each cover a cluster of cells, is represented as NWB. NWBis sufficiently large such that all the cells232within FOV230are covered by WBs with minimum overlapping. Typically, the signal channel bandwidth of a WB is BWIC. Whereas, the number of IABs plus the number of WBs is less than the number of IACs: (NiBC+NWB)<NIC. And, BWAC*NAC+BWIC*(NiBC+NWB)≤Total Gateway Beam Bandwidth. BWICcan be the minimum allowed channel bandwidth or the same bandwidth used for an active cell BWAC. When number of ACs and the channel bandwidths are given, the total bandwidth used by all beams can be controlled via adjusting the beamwidth of the WBs (i.e. the number of WBs NWB).

Beam212ashows a nominal beam (NB) covering an active cell (AC), and cell212bshows nominal beam (NB) covering an inactive cell (IAC).

The base station100of the present disclosure, and specifically the eNodeB120, provides network access management. In one embodiment of the disclosure, the base station100provides UE Access and Attachment, the operation of which is provided inFIG.5. Starting at step300, with reference toFIGS.1,4, the base station100uplinks the predetermined beamforming coefficients (based on the beamwidth for covering a cluster with a given number of cells, beam boresight, and sidelobe requirements) and the channel frequency/bandwidth to the satellite210via the feeder link152to allow the satellite210to form a set of one or more WBs214, each to cover a cluster of cells (may include one or more active cells)232. In one embodiment, the number of WBs214(NWB) is sufficient to cover the entire FOV230of a given satellite210. Each of the WBs214carries the same channel bandwidth as the active beam or the minimum channel bandwidth allowed in the operational band(s). The WBs214are the default beams until access request is identified within the cells illuminated by a given WB or WBs.

At step302, the WBs214broadcast the network information and timing synchronization signal and search/listen for an access signal requesting a connection, such as a Physical Random Access Channel (PRACH) in cellular system, from a potential User Equipment (UE), such as a cellphone. Low S/N requirements for PRACH and downlink timing synchronization signals allow wider beam-width beams214to be used. A UE or UEs may not be able to successfully attach to the network (such as eNodeB in 4G/LTE or gNB in 5G) associated to WB due to large differential delay and/or Doppler shift over the large cell as well as low S/N.

At step304, if no access signal is detected in response to the WBs214broadcast, the base station100returns to step300where it continues to monitor. When a UE or UEs, not belonging to any of the active cells (ACs) within the group, is detected by the eNodeB (or gNB) associated with a WB214, step304, one or more IABs212bare formed by the satellite120, via the beamforming coefficients and the beam boresight uplinked from the base station100, to cover all the IACs within the cluster of the cells covered by that WB to locate the UE(s) to a specific cell, step306. The frequencies and the signal bandwidths of the IABs can be the same as or different from the ones used by the WB314. At step306, the IAB212bwith the located UE(s) will stay and become an AB212ato allow the UE(s) to attach to the network and start communications; the remailing IABs212bwill be turned off and their channel bandwidth will become available to locate UEs in other groups. An AB212ashould be turned off when traffic is stopped. The process will repeat until the number of active beams reaches to the system limit (by the available gateway bandwidth). IABs are only used in the area covered by a WB or WBs where a UE or UEs has been detected by the eNodeB(s) (or gNB) associated with the WB(s) to minimize the gateway beam bandwidth usage.

At step308, if no access signal is detected by the base station100via an IAB212b, the base station100continues to monitor, step304. Once an access signal is detected, step308, the base station100tries to attach the UE(s) via the IAB, step310. If attachment is successful, step310, the IAB is added to the AB list, step312, and the IABs without an access signal returned off and the bandwidths are released in gateway links, step314, and the system returns to step300. If attachment is unsuccessful, step310, the base station100determines if it has reached the limit for the number of attempts to attach, step316. If the limit is reached, the IAB is also turned off and the bandwidths released, step314, and the system returns to step300. If the limit is not reached, further attempts are made, step310.

As a non-limiting example for 4G/LTE, the satellite illuminates the WB with a cluster of cells configured with a very short RAR (Random Access Response) window and the minimum number of PRACH attempts possible. The delay tolerant RAR modifications (that is essential for a standard UE to attach to the network) is not necessary for the WB. Next, the UE transmits a PRACH at To and if it doesn't receive a reply, sends a PRACH again until reaching the maximum number of attempts. The eNodeB via a satellite detects the PRACH and replaces the WB by the number of IABs, that is equal to the number of ICs covered by the WB, each with the default cell ID. These new cells send proactively the RAR, such as in U.S. patent Ser. No. 16/379,399, the entire contents of which are hereby incorporated by reference.

If the UE cannot attach to the original cell associated to the WB, it goes to search new cells. It should quickly find one in the same frequency since it is being illuminated by the new cells with IABs. The UE then tries to PRACH again to the new cell and can successfully attach (due to standard compliant differential delay and doppler shift related to the smaller cell and higher S/N ratio). The other IABs covering the cells within the coverage area of the WB are switched off.

In another embodiment of the disclosure, the base station100can provide UE Access and Attachment. All ABs212aand IABs212bare beams covering the same size cells. Each IAB carries the same channel bandwidth as an AB or the minimum channel bandwidth allowed in the operational band(s). Each IAB is switched repeatedly within a group of ICs and stays X seconds at each cell, broadcasting the downlink timing synchronization and searching/listening the PRACH. When a UE or UEs is detected in an IC by the eNodeB associated with an IAB, the beam will stay and become an AB to allow the UE(s) to attach to the network and start communications. The process will repeat until the number of ABs reaches to the system limit (limited by the total gateway beam bandwidth). This can be provided as an alternative to, or in addition to, the operation ofFIG.5.

Accordingly, the satellite communications system has a base station communicating with standard compliant user equipment (UE) via a satellite having a field of view. The base station has a processing device that generates (via the satellite) a first network broadcast/access signal which is communicated over a wide beam signal214A (FIG.4) covering a plurality of cells in the field of view. If needed, multiple wide beam signals can be sent to a different or overlapping plurality of cells, to cover the entire field of view of that satellite. In one embodiment, the wide beam signal can be a broadcast signal to all of the plurality of cells. One or more of those cells might be inactive (IAB)212B, that is there is no UE in that cell which is already attached to (i.e., in communication with) the base station. However, one or more of those cells might instead be active (AB)212A, that is there is at least one UE in that cell which is already attached to the base station. For each AB cell212A, there is an existing nominal beam signal already established with that cell to communicate with the connected UE.

The processor then detects (via the satellite) a new access request from a new UE within the plurality of cells over the wide beam signal. However, at this point, the base station processor does not know in which of the plurality of cells the new UE is located. It is noted that the new access request is likely coming from one of the IAB cells. If the new UE was in an AB cell, then it would connect with the base station through the existing nominal beam signal for that AB cell. Accordingly, in response to the new access request, the base station processor generates (via the satellite) a second network broadcast/access signal or signals that is sent over one or more nominal beams each covering one of the plurality of cells. That is, the second network access signal is sent over the new nominal beam signals for the IAB cell(s), and any existing AB cell will continue to use its own broadcast/assess signal which is unique for that active cell. The wide beam signal can continue at the same time the nominal beams are activated, since the nominal beam signals are either at different frequencies or much stronger than the wide beam signals and therefore the UE will send the access request through the nominal beam signals. In one embodiment, the wide beam signal can be deactivated when the nominal signals are activated. In one embodiment, the nominal beam signals can be at the same frequency as the wide beam signal, or can be at different frequencies.

The new UE will then respond to the second network broadcast/access signal by sending its access request on the nominal beam. The base station processor receives that response (via the satellite) and can determine which one of the plurality of cells has detected the UE access request, and in which cell the UE is located. Once the cell is identified, the processor attaches to the UE, adds that cell to the list of active cells (ACs) and start to communicate with the UE in that cell with data traffic. The network broadcast/access signals for the other nominal beams that covers the other cells (not containing the new UE) are ceased, and the system returns to generate an access signal over the wide band signal until a new UE network access request is detected. This minimizes the total bandwidth usage related to network broadcast/access request over the cells without existing connected UEs, because a nominal beam signal needs not be provided to each cell in the field of view. Rather, a plurality of wide beam signals can be provided to cover all of the plurality of cells in the field of view, and nominal beam signals can be provided for those cells in which a UE or UEs is currently communicating with the base station.

The system and method of the present disclosure can be implemented using standard UEs by computer software that accesses data from an electronic information source. The software and the information in accordance with the disclosure may be within a single processing device, such as at the eNodeB, or it may be in a central processing networked to a group of other computers or other electronic devices. The software and information may be stored on a medium such as a memory or data storage device. The entire process is conducted automatically by the processor, and without any manual interaction. A medium also includes one or more non-transitory physical media that together store the contents described as being stored thereon. In addition, unless indicated otherwise the process can occur substantially in real-time without any delay or manual action.

The description and drawings of the present disclosure provided in the paper should be considered as illustrative only of the principles of the disclosure. The disclosure may be configured in a variety of ways and is not intended to be limited by the preferred embodiment. Numerous applications of the disclosure will readily occur to those skilled in the art. For example, each nominal beam212has been described as being associated with a single cell232. However, the nominal beam212can be associated with more than one cell232or less than one entire cell232. Thus, for example, two nominal beams212can be provided for a single cell232. Or, a single nominal beam212can cover multiple cells232.

Therefore, it is not desired to limit the disclosure to the specific examples disclosed or the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.