Showing papers by "Rapeepat Ratasuk published in 2010"

LTE-advanced: next-generation wireless broadband technology [Invited Paper]

Abstract: LTE Release 8 is one of the primary broadband technologies based on OFDM, which is currently being commercialized. LTE Release 8, which is mainly deployed in a macro/microcell layout, provides improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operation and seamless integration with existing systems. LTE-Advanced (also known as LTE Release 10) significantly enhances the existing LTE Release 8 and supports much higher peak rates, higher throughput and coverage, and lower latencies, resulting in a better user experience. Additionally, LTE Release 10 will support heterogeneous deployments where low-power nodes comprising picocells, femtocells, relays, remote radio heads, and so on are placed in a macrocell layout. The LTE-Advanced features enable one to meet or exceed IMT-Advanced requirements. It may also be noted that LTE Release 9 provides some minor enhancement to LTE Release 8 with respect to the air interface, and includes features like dual-layer beamforming and time-difference- of-arrival-based location techniques. In this article an overview of the techniques being considered for LTE Release 10 (aka LTEAdvanced) is discussed. This includes bandwidth extension via carrier aggregation to support deployment bandwidths up to 100 MHz, downlink spatial multiplexing including single-cell multi-user multiple-input multiple-output transmission and coordinated multi point transmission, uplink spatial multiplexing including extension to four-layer MIMO, and heterogeneous networks with emphasis on Type 1 and Type 2 relays. Finally, the performance of LTEAdvanced using IMT-A scenarios is presented and compared against IMT-A targets for full buffer and bursty traffic model.

Carrier Aggregation in LTE-Advanced

Abstract: UMTS LTE system can support flexible bandwidth configuration up to 20 MHz. Currently, system enhancements are being considered to provide substantial improvements to LTE and allow it to meet or exceed IMT-Advanced requirements. One key enhancement feature is bandwidth extension via carrier aggregation to support deployment bandwidth up to 100 MHz. This will allow peak target data rates in excess of 1 Gbps in the downlink and 500 Mbps in the uplink to be achieved. Carrier aggregation is attractive because it allows operators to deploy a system with larger bandwidth by aggregating several smaller contiguous or non-contiguous carriers while providing backward compatibility to legacy users. For instance, an 80MHz system can be constructed using contiguous or non-contiguous 4×20MHz component carriers. Legacy users can then access the system using one of the component carriers. This paper provides an overview of carrier aggregation and discusses major technical issues including aggregation structure, scenarios, implementation, control signalling design and coexistence with legacy LTE systems.

Method and apparatus for downlink resource allocation in an orthogonal frequency division multiplexing communication system

Abstract: A communication is provided that schedules both Distributed Virtual Resource Blocks (DVRB) and Localized Virtual Resource Blocks (LVRB) in a same frequency channel, thereby obtaining the benefits of frequency selective scheduling while minimizing the uplink feedback overhead. In one embodiment of the invention, the communication system assigns one or more downlink Physical Resource Blocks (PRBs) of multiple downlink Physical Resource Blocks (PRBs) to each user equipment (UE) given an LVRB to produce at least one reserved PRB and multiple non-reserved PRBs and assigns a part of each PRB of the multiple non-reserved PRBs to a UE given a DVRB. In another embodiment of the invention, the communication system assigns PRBs pre-reserved for localized transmission to UEs scheduled for LVRBs and assigns parts of multiple PRBs pre-reserved for distributed transmission to each UE given a DVRB.

Method and apparatus for providing contention-based resource zones in a wireless network

Abstract: A base station employs control signaling for contention-based uplink access from user equipment devices to the base station. Contention-based access configuration is performed via physical downlink control channel signaling. Configuration data sent to the user equipment devices identifies (502) multiple contention-based access zones, along with minimum power headroom values (506) for each contention-based access zone. A probability factor (508) may be used to lower collision possibility by influencing whether the user equipment devices perform contention-based uplink access.

Method and apparatus for channel sounding in an orthogonal frequency division multiplexing communication system

Abstract: An Orthogonal Frequency Division Multiplexing communication system (200) is provided that triggers a transmission of an uplink sounding signal by use of a Downlink Control Information (DCI) message (600, 700) In various embodiments of the invention, the DCI message may be used to individually trigger an uplink sounding signal by a single user equipment (202) or may be used to trigger an uplink sounding signal by a group of users equipment (202-204)

Uplink power control for channel aggregation in a communication network

Abstract: A system and method for uplink power control for aggregated channels in a communication network includes a step 300 of defining power scaling parameters to be used to derive power scaling factors to be applied to associated aggregated uplink channels. A next step 302 includes providing the power scaling parameters to user equipment. A next step 304 includes applying power scaling factors derived from the power scaling parameters to the associated aggregated uplink channels when the user equipment will exceed a maximum transmit power.

Method and apparatus for scheduling a controlchannel in an orthogonal frequency division multiplexing communication system

Abstract: A scheduler capable of operating in an Orthogonal Frequency Division Multiplexing communication system schedules a control channel for a user equipment by determining a channel quality metric associated with the user equipment, calculating a target control channel element quality metric, determining a control channel element utilization rate, wherein the control channel element utilization rate a past rate of utilization of control channel elements, and selecting a control channel element aggregation level for the control channel based on the channel quality metric, the target control channel element quality metric, and the control channel element utilization rate. The scheduler then allocates control channel elements to the control channel based on the selected control channel element aggregation level. The scheduler further may steal power from one or more unused control channel elements and assign the stolen power to control channel elements assigned to the control channel.

Method and apparatus for determining when to use contention-based access for transmitting data in a wireless network

Abstract: A wireless communication system as described here employs control signaling for contention-based uplink access from user equipment devices to a base station. Contention-based access configuration is performed via physical downlink control channel signaling. Configuration data sent to the user equipment devices identifies multiple contention-based access zones, along with minimum power headroom values for each contention-based access zone. A probability factor may also be used to lower collision possibility by influencing whether the user equipment devices perform contention-based uplink access. An uplink grant message can be used to acknowledge contention-based transmission; contention resolution is achieved implicitly via the uplink grant.

Method for uplink acknowledgment/non-acknowledgment messages in a wireless communication system

Abstract: A method for uplink ACK/NACK for LTE TDD. The method includes receiving a frame having multiple subframes wherein a plurality of subframes being downlink subframes and at least one subframe being an uplink subframe. One uplink subframe can contain an acknowledgment/non-acknowledgment (ACK/NACK) corresponding to at least one of the plurality of downlink subframes. To transmit ACK/NACKs, one uplink subframe for ACK/NACK is used in response to one of the plurality of downlink subframes. In addition, ACK/NACK responses can be bundled into one uplink subframe for at least two of the plurality of downlink subframes. In an embodiment, multiple ACK/NACK responses can be used in one uplink subframe that corresponds to at least two of the plurality of downlink subframes in a multiple feedback configuration. One uplink subframe for ACK/NACK responses and bundling multiple ACK/NACK responses is for a bundled feedback configuration.

Method for signaling a mobile wireless device to switch to a preset carrier in a multi-carrier 4G network

Abstract: A method, a system and an evolved nodeB (eNodeB) that enable user equipment (UE) to switch between carrier groups in a multi-carrier network. A carrier selection and switching (CSS) utility identifies a first and a second set of pre-configured groups of carrier frequencies that are subsequently assigned to a particular UE. The CSS utility notifies the UE of the assigned, pre-configured groups of carrier frequencies and provides the UE with system parameters associated with the first and second pre-configured groups of carrier frequencies. The CSS utility signals the UE to initiate communication via the first preconfigured group of carriers. Based on the occurrence of pre-established conditions, the CSS utility utilizes a switch signal to indicate via physical downlink control channel (PDCCH) to the UE (a) when to begin utilizing the second group of preconfigured carrier frequencies and (b) when to make subsequent switches between carrier groups.

Satisfying a delay requirement for a delay sensitive data connection

Abstract: A method to satisfy a delay requirement for a delay sensitive data connection through a scheduling, the method comprising: setting a discard timer for the delay sensitive data connection; determining an age of a packet corresponding to the delay sensitive service in a priority queue; performing a comparison between the age of a most recently successfully transmitted or time expired data packet with the discard timer setting, to determine whether the age of the compared packet is less than the discard timer setting by a predetermined margin; and calculating a new delay factor for the delay sensitive data connection based on the comparison and an old delay factor of the delay sensitive data connection. Aspects of the invention include the calculating step further comprising setting the new delay factor to a value obtained by increasing the old delay factor by a first predetermined factor and dropping the oldest packet if the age of the oldest packet is not less than the discard timer by a predetermined margin.