Enhanced local access in mobile communications with FDD resource allocation

#This application is directed to the operation of the Physical and Link Layers in mobile communication protocols.

#One option to increase capacity in a wireless network is to increase the density (number of devices per unit area) of deployed base stations or remote antenna units. If the density of the deployed base stations or remote antenna units increases, cell capacity increases due to frequency reuse effects. However, there are some difficulties that come with increasing the deployment density, especially if such deployed units must be able to operate as conventional base stations on their own. These difficulties include: 1) As the deployment density increases, the number of handovers increases because the user equipment changes its serving unit (base station) quite frequently. As a result, quality of connectivity/mobility is expected to be degraded. Thus, the deployed unit for increasing cellular capacity should have high-quality interworking with the macro base station. 2) The conventional macro base stations transmit some required signals, such as pilot signals, synchronization signals, broadcast signals, paging signals, and so on, all of which have the potential to cause interference problems. Such interference limits the number of deployed base stations and thus lowers cellular capacity. 3) Furthermore, radio resources for the required conventional macro base station signals are typically static. Thus, dynamic and efficient interference coordination through dynamic allocation of the radio resources is difficult, which also limits the number of the deployed base stations and associated cellular capacity. 4) Network operators need to assign cell ID or other cell-specific parameter to each cell. For example, the root sequences for random access channels in LTE uplink (UL) are an example of such cell-specific parameters. Such cell planning for the cell ID, the root sequences and the like is cumbersome, which also limits the number of the deployed base stations and associated cellular density. 5) The required cell capacity is region-specific. For example, a significantly large capacity is required in urban areas whereas a relatively small enhancement of cell capacity may be sufficient in suburban or rural areas. To efficiently satisfy such divergent density needs, the deployed unit should be easily installed with low cost/complexity 6) If the cost of each deployed unit is high, the total system cost is quite high as the deployment density increases. Thus, the deployed unit cost should be relatively low to feasibly increase cell capacity.

#Various architectures have thus been proposed to increase wireless network capacity. For example, distributed base stations using the Remote Radio Head (RRH) technology communicate with a base station server using optical fiber. Because the base station server performs the baseband processing, each RRH distributed base station thus acts as a power amplifier with regard to its base station server. As the density of the RRH distributed base stations is increased, the baseband processing complexity is increased at the base station server. Thus, the number of RRH cells corresponding to each distributed RRH base stations is limited due to this baseband complexity.

#FIG. 1a is an example architecture for an enhanced local area radio access system using advanced user equipment.

#FIG. 1b is an example architecture for an enhanced local area radio access system using small-node devices.

#FIG. 2 annotates the data paths in the system of FIG. 1b for a given one of the small-node devices.

#To address the prior art drawbacks discussed above, the applicant has developed two innovative network architectures. These architectures are described in International Application No. PCT/US12/48690, filed May 31, 2012 and in International Application No. PCT/US12/40288, also filed May 31, 2012. The contents of both of these applications are hereby incorporated by reference in their entirety. The first architecture uses a novel network device denoted as an advanced user equipment (UE-A). The UE-A shares a number of features in common with conventional user equipment (UE). The common structural elements and function thus conveniently lower the manufacturing costs associated with a UE-A. Although a UE-E has assorted features in common with a user equipment (UE), it will be appreciated that, with respect to a UE, a UE-A may be a network-side device analogous to a base station or other network-side node. Alternatively, the UE-A may be a UE-side device. In contrast to a conventional UE, the UE-A of the first architecture allows offloading of data traffic that would otherwise have to be carried by the link between the macrocell base station and the UE. The UE-A has a backhaul link to the core network and/or the Internet to accommodate the offloaded data. In turn, a UE-A-to-UE link carries the offloaded data between the UE-A and the UE in both the uplink (UL) and downlink (DL) directions. This UE-A-to-UE link may be denoted as a D2UE link whereas a base-station-to-UE link may be denoted as a Macro2UE link. A link between the base station and the UE-A may be denoted as a Macro2D link. In one embodiment, both the Macro2UE and Macro2D links may be LTE links. The base station controls the establishment of the D2UE link through the base-station-to-UE-A link and/or through the Macro2UE link.

#In an LTE embodiment, the LTE links (the Macro2UE and Macro2D) links may operate at 2 GHz whereas the D2UE link operates at a different frequency such as, for example, 3.5 GHz. In this fashion, the UE utilizes carrier aggregation. Such an embodiment has the advantage of the combined bandwidth from the carrier aggregation and the associated inter-carrier interference mitigation. Alternatively, the Macro2D, Macro2UE, and D2UE links may all operate in the same frequency band. Regardless of the particular embodiment, a network according to the first architecture has the advantage that the establishment, reconfiguration, release, or handoff of the D2UE link is under the control of the base station (or a higher-level network node). Thus, the UE-A construction and operation is greatly simplified. To better appreciate the advantages of the data offloading provided by a UE-A, it is useful to compare the resulting data offloading to that achieved in the prior art.

#For example, a remote radio head (RRH) is a conventional network node that offloads data that would otherwise have to be carried by the base station to (and from) the UE. But an RRH is effectively just a power amplifier such that it has no baseband processing. The base station must then perform the RRH baseband processing, which burdens the base station operation and hinders the use of a plurality of RRHs throughout the corresponding macrocell. In contrast, the UE-A performs its own baseband processing. Thus, the first network architecture enables a macrocell to include a plurality of UE-As, which greatly increases the data-offloading coverage within the macrocell.