WO2013131258A1

WO2013131258A1 - Apparatus and methods for fast dl cc broken determination and recovery for unlicensed band lte

Info

Publication number: WO2013131258A1
Application number: PCT/CN2012/072062
Authority: WO
Inventors: Gilles Charbit; Wei Hong; Wei Bai; Na WEI; Erlin Zeng; Haiming Wang; Pengfei Sun; Chunyan Gao
Original assignee: Renesas Mobile Corporation
Priority date: 2012-03-07
Filing date: 2012-03-07
Publication date: 2013-09-12

Abstract

A method to determine and recover from broken DL CC for unlicensed band LTE systems is described. The method includes determining, at a mobile device, whether a first DL CC on an unlicensed band is broken. In response to determining that the first DL CC is broken, an UL CC on the unlicensed band is selected based at least in part on the first DL CC and, a message including an indication that the first DL CC is broken is transmitted from the mobile device on the UL CC. The method includes receiving the message at the access node. The method also includes, in response to receiving the message, selecting at least one DL CC on the unlicensed band and transmitting recovery information from the access node on the at least one DL CC. Apparatus and computer readable media are also described.

Description

APPARATUS AND METHODS FOR FAST DL CC BROKEN

DETERMINATION AND RECOVERY FOR UNLICENSED BAND LTE

TECHNICAL FIELD:

The exemplary and non-limiting embodiments relate generally to wireless communication systems, methods, devices and computer programs and, more specifically, relate to determining and recovering from broken DL CC for unlicensed band LTE systems. BACKGROUND:

This section is intended to provide a background or context to what is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.

The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:

3 GPP third generation partnership project

ARFCH absolute radio frequency channel

BCCH broadcast control channel

BDI broken DL CC information

BW bandwidth

CC component carrier

CCE control channel element

CDM code division multiplexing

CRC cyclic redundancy check

CRS common reference signal

DCF distributed coordination function DCI downlink control information

DL downlink (eNB towards UE)

DRX discontinuous reception

eNB E-UTRAN Node B (evolved Node B)

EPC evolved packet core

E-UTRAN evolved UTRAN (LTE)

HARQ hybrid automatic repeat request

IMT-A international mobile telephony-advanced

ITU international telecommunication union

ITU-R ITU radiocommunication sector

LTE long term evolution of UTRAN (E-UTRAN)

LTE-A LTE Advanced

MAC medium access control (layer 2, L2)

MIB master information block

MM/MME mobility management/mobility management entity

Node B base station

O&M operations and maintenance

OFDMA orthogonal frequency division multiple access

P-BCH physical broadcast channel

PCC primary cell carrier

PDCP packet data convergence protocol

PDSCH physical downlink shared channel

PHY physical (layer 1, LI)

P-SCH primary synchronization channel

PUCCH physical uplink control channel

REG resource element group

RLC radio link control

RLF radio link failure

RMB recovery message block

RRC radio resource control

RRH remote radio head RRM radio resource management

SCC secondary cell carrier

SC-FDMA single carrier, frequency division multiple access

SFN system frame number

S-GW serving gateway

SIB system information block

S-SCH secondary synchronization channel

TCC tracking component carrier

UCI UL Control Information

UE user equipment, such as a mobile station or mobile terminal

UL uplink (UE towards eNB)

UTRAN universal terrestrial radio access network

As is specified in 3 GPP documents, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of prior LTE releases (e.g., up to 100MHz) to achieve the peak data rate of lOOMbit/s for high mobility and 1 Gbit/s for low mobility. Carrier aggregation, where two or more component carriers (CCs) are aggregated, may be used in order to support transmission bandwidths larger than 20MHz. The carrier aggregation could be contiguous or non-contiguous. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation.

A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. A legacy terminal might receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the relevant specifications. Moreover, it is required that LTE-A should be backwards compatible with older standards in the sense that a legacy terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system. Figure 1 shows an example of the carrier aggregation, where M 20MHz component carriers are combined together to form M <20 Hz BW (e.g., 5 x 20MHz = 100MHz given M = 5). Legacy terminals may receive/transmit on one component carrier, whereas LTE-A terminals may receive/transmit on multiple component carriers simultaneously to achieve higher (wider) bandwidths,

With further regard to carrier aggregation, what is implied is that one eNB can effectively contain more than one cell on more than one CC (frequency carrier), and the eNB can utilize one (as in E-UTRAN Rel-8) or more cells (in an aggregated manner) when assigning resources and scheduling the UE.

A licensed spectrum band, supervised by operators, is a scarce resource. The scarcity of this resource along with the current licensed spectrum policy, having limited to no flexible spectrum usage, may not be enough to support a larger number of cellular devices and higher-QoS traffic in the near future. Therefore, traffic off-loading to unlicensed band, e.g., a TV white space (TVWS) band, may be an attractive solution for cellular operators,

Figure 2 is an illustration of the regulatory requirements on the TVWS bands. As shown, the bands are separated in to various TV channels 200. Of the limited channels shown, there is a low VHF band 202 covering channels 2-6; a high VHF band 204 covering channels 7-13 and an UHF band 206 covering channels 14-51 (this band extends beyond channel 51). Some channels 310 are only allowed to be used for DL transmission (fixed devices only) and some of these channels are only allowed to be used for UL transmission (e.g., channels which are adjacent to TV channel). Other channels 230 are allowed for communications between a fixed device while yet other channels 240 are not allowed. When using these kinds of carriers, frequency division duplexing (FDD) may be utilized. LTE has been mainly designed to operate in licensed bands, where the channel is dedicated to the LTE system under regulation. However, deploying LTE in unlicensed bands has been contemplated lately in order to further enhance the LTE performance by utilizing the unlicensed band for additional bandwidth. The unlicensed band does not include license restrictions and, thus, may be shared by different radio access technology (RAT) devices. This shared band deployment has the potential to bring LTE many benefits such as:

• Low cost: Given that no license is required, the extra spectrum will be gained with much lower cost;

* Flexible deployment: Similarly, as no license is mandatory in these shared bands, the system can be deployed in a flexible manner regardless of the need and application; and

New applications: The deployment in unlicensed band is more of an ad-hoc style compared with to the cellular infrastructure of LTE system on the licensed band. Therefore new applications can be devised in the field such as monitoring, control, telemetry, etc.

By the way of utilization the shared band, the LTE implementations can be divided into two categories: 1) a standalone utilization, where the whole LTE system is operating in shared bands; and 2) a hybrid utilization, where both licensed bands and unlicensed bands are available for the LTE system. In the hybrid utilization the LTE system may adopt dynamic strategies to utilize both types of bands.

Based on this categorization, it is expected that shared band LTE systems will face different operating scenarios to LTE systems that use only licensed bands, for example, frequent PCell breaks when deploying standalone LTE systems in TVWS with a FDD mode. Furthermore, because TV channels below channel 20 are only used for fixed devices, these channels may be used as FDD DL CCs. Due to the larger transmission power of fixed devices and better propagation characteristics of these DL only channels, there is a chance that some FDD DL CCs may be broken while other FDD UL CCs are not broken.

On unlicensed bands, for a standalone LTE system using FDD, there is a chance that the downlink component carrier (DL CC) or uplink component carrier (UL CC) is broken due to a number of causes. For example, the ON/OFF pattern used by the LTE system to share the resource with other systems operating on the unlicensed band, interference from other RAT devices, and various regulation requirements. When a LTE DL CC in the unlicensed band is broken this can cause a physical downlink control channel (PDCCH) error for certain UEs. With such an error, it is hard for the UE to decode information such as DL or UL grants.

Conventional techniques attempt to determine a DL CC break, also referred to as radio link failure (RLF). In some, the UE measures a common reference signal (CRS) which is sent by an eNB. The UE uses the CRS to get the related DL channel quality for each radio frame or each discontinuous reception (DRX) cycle. If the measurement result is worse than a given threshold, the UE interprets the result as a RLF and trigger the further action. The UE may respond at a PHY layer and/or at a RRC layer.

In the PHY layer, if the UE is in a non-DRX mode, the physical layer in the UE is expected, in every radio frame, to assess the radio link quality, evaluated over a time period, against thresholds (e.g., Q_out and Q_m). If the UE is in a DRX mode, the physical layer in the UE is expected, in at least once every DRX period, to assess the radio link quality, evaluated over a time period, against thresholds (Q_out and Qj_n).

In the RRC layer, the UE is expected to consider radio link failure to be detected in response to any one of: an expiration of a timer, upon receiving a random access problem indication from the MAC while certain timers are not running; or upon receiving a indication from the RLC that a maximum number of retransmissions has been reached.

If the DL CC or DL PCell is severely interfered, a RLF will be triggered and the UE will initialize a RRC re-establishment procedure. During the RRC re-establishment, the UE can reset the MAC configuration and the PHY configuration as well as perform cell reselection, system information reading, random access, etc. However, before the UE performs such actions, the eNB does not know the channel condition of the given DL CC since there will be no available UL channel.

Some procedures enable a fast synchronization and fast SCC activation at the beginning of an ON duration of a DL CC, e..g., using a fast synchronization verification block mapped to the transport channel BCCH or transport channel DL-SCH. However, there is no method for providing a broken CC indication to the eNB. What is needed is a technique to determine and recover from broken DL CC for unlicensed band LTE systems quickly.

SUMMARY

The below summary section is intended to be merely exemplary and non-limiting. The foregoing and other problems are overcome, and other advantages are realized, by the use of the exemplary embodiments.

In a first aspect thereof an exemplary embodiment provides a method to determine and recover from broken DL CC for unlicensed band LTE systems. The method includes determining, at a UE, whether a first DL CC on an unlicensed band is broken. The method includes, in response to determining that the first DL CC is broken, selecting an UL CC on the unlicensed band based at least in part on the first DL CC and transmitting, from the UE on the UL CC, a message including an indication that the first DL CC is broken.

In another aspect thereof an exemplary embodiment provides a method to determine and recover from broken DL CC for unlicensed band LTE systems. The method includes receiving, at an eNB on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken. The method also includes, in response to receiving the message, selecting at least one DL CC on the unlicensed band and transmitting recovery information from the eNB on the at least one DL CC. In a further aspect thereof an exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes a processor and memory storing computer program code. The memory and the computer program code are configured to, with the processor, cause the apparatus to perform actions. The actions include to determine, at a UE, whether a first DL CC on an unlicensed band is broken. The actions also include, in response to determining that the first DL CC is broken, to select an UL CC on the unlicensed band based at least in part on the first DL CC and to transmit, from the UE on the UL CC, a message including an indication that the first DL CC is broken.

In another aspect thereof an exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes a processor and memory storing computer program code. The memory and the computer program code are configured to, with the processor, cause the apparatus to perform actions. The actions include to receive, at an eNB on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken. The actions also include, in response to receiving the message, to select at least one DL CC on the unlicensed band and transmitting recovery information from the eNB on the at least one DL CC.

In a further aspect thereof an exemplary embodiment provides a computer readable medium to determine and recover from broken DL CC for unlicensed band LTE systems. The computer readable medium is tangibly encoded with a computer program executable by a processor to perform actions. The actions include determining, at a UE, whether a first DL CC on an unlicensed band is broken. The actions also include, in response to determining that the first DL CC is broken, selecting an UL CC on the unlicensed band based at least in part on the first DL CC and transmitting, from the UE on the UL CC, a message including an indication that the first DL CC is broken.

In another aspect thereof an exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes means for determining, at a UE, whether a first DL CC on an unlicensed band is broken. The apparatus includes means for selecting an UL CC on the unlicensed band based at least in part on the first DL CC in response to determining that the first DL CC is broken and means for transmitting, from the UE on the UL CC, a message including an indication that the first DL CC is broken.

In a further aspect thereof an exemplary embodiment provides a computer readable medium to determine and recover from broken DL CC for unlicensed band LTE systems. The computer readable medium is tangibly encoded with a computer program executable by a processor to perform actions. The actions include receiving, at an eNB on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken. The actions also include, in response to receiving the message, selecting at least one DL CC on the unlicensed band and transmitting recovery information from the eNB on the at least one DL CC.

In another aspect thereof an exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes means for receiving, at an eNB on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken. The apparatus also includes means for selecting at least one DL CC on the unlicensed band in response to receiving the message and means for transmitting recovery information from the eNB on the at least one DL CC.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects of exemplary embodiments are made more evident in the following Detailed Description, when read in conjunction with the attached Drawing Figures, wherein:

Figure 1 shows an example of carrier aggregation as proposed for the LTE-A system.

Figure 2 is an illustration of the regulatory requirements on the TVWS bands.

Figure 3 shows a simplified block diagram of exemplary electronic devices that are suitable for use in practicing various exemplary embodiments.

Figure 4 shows a simplified block diagram of a component carrier ON-OFF pattern.

Figure 5 is a signaling diagram that illustrates the operation of an exemplary embodiment.

Figure 6 is a logic flow diagram that illustrates the operation of an exemplary method, and a result of execution of computer program instructions embodied on a computer readable memory, in accordance with various exemplary embodiments.

Figure 7 is another logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions, in accordance with an exemplary embodiment.

DETAILED DESCRIPTION

Various embodiments are suitable for a standalone LTE system operating in an unlicensed band. A mobile device (e.g., a UE) in the system can perform a fast DL CC break determination and report the break to an access node (e.g., the eNB). The mobile device can determine which CC to use to report the break based on the type of CC that is broken (or otherwise unsuitable for use). This improves the chances that the reporting will be properly received at the access node. Once the access node receives the information, the system can take actions to quickly recovery following the broken CC.

Before describing in further detail various exemplary embodiments, reference is made to Figure 3 for illustrating a simplified block diagram of various electronic devices and apparatus that are suitable for use in practicing exemplary embodiments.

In the wireless system 330 of Figure 3, a wireless network 335 is adapted for communication over a wireless link 332 with an apparatus, such as a mobile communication device which may be referred to as a UE 310, via a network access node, such as a Node B (base station), and more specifically an eNB 320. The UE 310 includes a controller, such as a computer or a data processor (DP) 314, a computer-readable memory medium embodied as a memory (MEM) 316 that stores a program of computer instructions (PROG) 318, and a suitable wireless interface, such as radio frequency (RF) transceiver 312, for bidirectional wireless communications with the eNB 320 via one or more antennas and/or via one or more radio access technologies (RATs). The eNB 320 also includes a controller, such as a computer or a data processor (DP) 324, a computer-readable memory medium embodied as a memory (MEM) 326 that stores a program of computer instructions (PROG) 328, and a suitable wireless interface, such as RF transceiver 322, for communication with the UE 310 via one or more antennas and/or via one or more radio access technologies (RATs).

At least one of the PROGs 318 and 328 is assumed to include program instructions that, when executed by the associated DP, enable the device to operate in accordance with exemplary embodiments, as will be discussed below in greater detail.

That is, various exemplary embodiments may be implemented at least in part by computer software executable by the DP 314 of the UE 310; and/or by the DP 324 of the eNB 320, or by hardware, or by a combination of software and hardware (and firmware).

The UE 310 and the eNB 320 may also include dedicated processors, for example CC processor 315 and CC processor 325.

In general, the various embodiments of the UE 310 can include, but are not limited to, cellular telephones, tablets having wireless communication capabilities, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.

The computer readable MEMs 316 and 326 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DPs 314 and 324 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multicore processor architecture, as non-limiting examples. The wireless interfaces (e.g., RF transceivers 312 and 322) may be of any type suitable to the local technical environment and may be implemented using any suitable communication technology such as individual transmitters, receivers, transceivers or a combination of such components.

A DL CC can be quickly determined as being broken using a timer. A UE may use a timer for each CC being monitored. The broken DL CC Break Timer can be predefined via higher layer signaling for the PCC and the SCC respectively. For example the UE may received parameters (e.g., T_DLcc-pcc and TDLCC-SC_C) which define how long the UE is to wait in case it does not receive control signaling on the PCC or the SCC on the unlicensed band. When a timer expires the UE concludes that a DL CC break has occurred on the associated CC. The control signaling may be a PCFICH, PDCCH/PDSCH, PBCH, PHICH, PMCH, etc. Additionally, the UE may set a timer and monitor the CC for a control format indicator, e.g., one encoded with 1/16 rate block code and mapped to a PCFICH.

If however, the UE receives control signaling on the CC, the timer may be reset (e.g., to TDLCC-PC_C or TDLCC-SCC)- The UE may maintain separate timers for each CC, for example, a first timer for the PCC and a second timer for the SCC. Each timer may be reset based on control signaling received on the associated CC.

Once the UE has determined that a CC is broken the UE can send a message to the eNB in order to report the broken DL CC. The message includes broken DL CC information (BDI).

If the broken DL CC is the SCC, the UE sends the BDI to the eNB on the PCC UL. The UE may use a MAC control element (CE) via dedicated signaling or use an UCI format on the PUCCH based on the UL grant. The UL grant may be received via LI signaling. If the broken DL CC is the PCC (or if both the PCC and SCC are broken), the UE sends the BDI to the eNB via fast LI signaling on the PUCCH. The LI signaling may have a periodicity (which may be configured via higher-layer on an "un-broken" UL CC). The BDI may be sent on higher-layer configured PUCCH resources on PCC UL, or in case PCC UL is broken, the BDI may be sent on the SCC UL. The BDI may be included in a scheduling request type of PUCCH to indicate broken DL CC. The BDI may include a suggested DL replacement CC index. The UE may also set a DL CC recovery timer (e.g., To_Lcc_rec) when sending the

BDI. The recovery timer value may have been configured via higher layer signaling. If UE does not receive recovery information before the recovery timer expires, the UE may resend the LI indication signaling to the eNB using the PCC UL. The UE may determine that the PCC UL is broken if the UE does not receive recovery information from the eNB, for example, if recovery information is not received after a given number of retries on the PCC UL or based on a second timer. In such a case, the UE may use the SCC UL. A UE may be configured by higher layer signaling to transmit a broken DL CC information report (BDIR) on one antenna port or two antenna ports. The BDIR can be transmitted on PUCCH resource(s) Κρϋΐ Η ⁼ "PUCCH,BDIRI f°^r antenna port p, where " UCCH. BDIRI ^s configured by higher layer signaling. The BDIR configuration for BDIR transmissions includes a periodicity parameter e.g., BDIRpERioDiciTY, and a BDIR subframe offset parameter, NOFFSET.BDIR- These configurations may be defined by a parameter, e.g., bdir-Configlndex I_BD!R which may also be provided by the higher layer signaling in order to indicate the periodicity and offset to use. The parameters may re-using similar values as specified for a scheduling request (SR) procedure. Table 1 illustrates some BDIR configuration parameter pairings. The BDIR transmission instances may be set to those that are uplink subframes satisfying the following equation:

I¹0 x n_f + [n, 12 J - N_0FFSETtBDlR Jmod BDIR_{p 0D!cm} = 0 , [ 1 ] where n_f is the System frame number and n_s is a slot number within a radio frame. The bdir-Configlndex I_BDIR may be configured to allow several BDIR transmissions within an ON duration on each UL CC.

Table 1 : UE-specific BDIR periodicity and subframe offset configuration

The ON duration for an UL CC may be signaled by the eNB once the eNB determines the duration to use. The determination can be done via interference measurements at the eNB receiver based on a failure of UEs to transmit various signals, e.g., a periodic CQI, a periodic SR, or a periodic sounding reference signals on UL resources configured via higher layer signaling (e.g., not via UL grant on the DO format, since a broken CC may also lead to the UE failing to transmit on DCI-linked UL resources).

The UE may try to send the BDI report on the PCC UL and report the broken CC index value and replacement CC index value. If the PCC UL transmissions are not successful, the UE may try again on the SCC UL. If still not successful, the UE may try to re-synchronize on any "un-broken" DL CC, as would be the case following a Radio Link Failure. For example, for PUCCH format 3, the payload size can be up to 20 bits. Then the broken CC index value and replacement CC index value can be quantized to a few bits for reporting. Once the eNB receives the BDI (either through the PCC UL, SCC UL, LI signaling, etc.), the eNB may attempt to repair the broken CC. The eNB may then send recovery information to the affected UE(s). The recovery information may be sent on a broadcast control channel (BCCH) or on a downlink shared channel on an un-broken CC. The recovery information may be indicated by the eNB in a recovery message block (RMB) that provides configuration information for the DL CCs which the UE is to check after determining (and reporting) a broken DL CC. The RMB may include an absolute radio frequency channel number of a group of DL CCs, an ON-OFF pattern based on subframe number for the CCs in the group of DL CCs, a bitmap indicating the broken/unbroken DL CCs (e.g., using a '0' bit to indicate broken CCs and a T bit to indicate un-broken CCs), and/or values for various timers (e.g., TDLCC-P_CO TDU -_SCO

TDLCC-rec, etc.).

Figure 4 shows a simplified block diagram of a component carrier ON-OFF pattern 400. Four channels are shown, channel 1 (401), channel 2 (402), channel 3 (403) and channel 4 (404). These channels may be distributed across the unlicensed band. In each subframe 420 (T1-T9) a channel is indicated as being ON (dark block 410) or OFF (light block 415). This pattern may be selected in order to share the channel with other RAT systems. The eNB may use the channels as either the PCC or SCC (e.g., channel 1 (401) may be used as the PCC and channel 2 (402) may be used for the SCC).

The RMB may be mapped to physical channel channels. The eNB can send the RMB on (some or all) unbroken DL carriers. The UE checks all DL CC that may be used by the eNB until the UE receives the RMB. If the eNB sends the RMB on all "unbroken" carriers, then the UE can get info faster. The UE may know which DL C may be used by eNB via higher-layer configuration. If a DL CC is broken, it may be for a single UE, a few UEs or all UEs, When the eNB determines that the DL CC is broken for all (or most) of the UEs attached to the eNB cell on unlicensed band, the RMB may be transmitted on a Physical Broadcast Channel (P-BCH) with a periodicity matching that of a P/S-SCH, for example, the RMB may be transmitted in a subframe containing both the P-SCH and S-SCH, A master information block (MIB) may also be transmitted on the P-BCH, e.g., with periodicity 40 ms in subframe #0 on four consecutive radio frames starting at SFN mod 4 = 0. If the MIB is to be transmitted in a transport block, the eNB may prevent transmitting the RMB in the same bloc, for example, no RMB is in subframe #0 in four consecutive radio frames stating at SFN mod 4 = 0. This avoids having to de-multiplexing the RMB and MIB if transmitted on the same transport block.

If, on the other hand, the eNB determines that the DL CC is broken for a small number (or one) of the UEs attached to the eNB cell on unlicensed band, the RMB may be transmitted via PDSCH resources. These PDSCH resources may be predefined, for example, by higher layer signaling. The cyclic redundancy check (CRC) of a PDCCH giving the DL grant may be scrambled with a UE-specific C-RNTI or a UE group RNTI. The DL grant may be used to indicate resources used for the RMB. The UEs receiving the DL grant may use the CRC to determine that the UE is an intended target (e.g., by having a C-RNTI/UE group RNTI matching the one used to scramble the CRC).

The advantage of using RMB mapped to a downlink shared channel is the use of an ACK as a confirmation of the recovery message. A UE may send an ACK to the eNB on PUCCH resources (which may be configured via higher layer signaling) after receiving the RMB. This enables the eNB to quickly determine that a UE cannot be scheduled (e.g., by not receiving an ACK from that UE). A PDSCH detection is expected to fail before a LI control signaling (for example, when using a robust P/S-SCH and MIB). The eNB can improve the reliability of a PDSCH by increasing the resources (e.g., by using a lower coding rate, lower operation point, etc.). The PDSCH resources may also be configurable via higher layer signaling.

Figure 5 is a signaling diagram that illustrates the operation of an exemplary embodiment. At 510, the eNB 502 sends control signaling on a PCC to the UE 504. Upon receiving the control signaling, the UE 504 starts a timer (e.g., a DL CC break timer for the PCC) at 515. At 520, the eNB 502 sends another control signaling on the PCC. Upon receiving the control signaling, the UE 504 resets the timer at 525.

At 530, the UE 504 has not received additional control signaling and the timer elapses. In response, the UE 504 sends BDI to the eNB 502 on CC serving as a PUCCH at time 535. The eNB 502, now informed of the broken PCC, sends a RMB on unbroken DL CC at time 540 (for example, where the UE 504 is the only UE affected).

After sending the BDI, the UE 504 begins checking DL CC for the RMB at time 545. Note that the UE 504 may begin searching for the RMB prior to the eNB 502 transmission of the RMB. Similarly, the UE 504 may wait before beginning to search for the RMB. Once the RMB is received, the UE 504 sends an acknowledgement (ACK) to the eNB 502 on the PUCCH. Based on the foregoing it should be apparent that the exemplary embodiments provide a method, apparatus and computer program(s) to determining and recovering from broken DL CC for unlicensed band LTE systems.

Figure 6 is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions, in accordance with an exemplary embodiment. In accordance with these exemplary embodiments a method performs, at Block 610, a step of determining, at a mobile device (e.g., a UE), whether a first DL CC on an unlicensed band is broken. In response to determining that the first DL CC is broken, the method performs, at Block 620, a step of selecting an UL CC on the unlicensed band based at least in part on the first DL CC and, at Block 630, performing a step of transmitting, from the mobile device on the UL CC, a message comprising an indication that the first DL CC is broken.

Figure 7 is another logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions, in accordance with an exemplary embodiment. In accordance with these exemplary embodiments a method performs, at Block 710, a step of receiving, at an access node (e.g., an eNB) on an UL CC on an unlicensed band, a message comprising an indication that a first DL CC on the unlicensed band is broken. In response to receiving the message, the method performs, at Block 720, a step of selecting at least one DL CC on the unlicensed band and, at Block 730, a step of transmitting recovery information from the access node on the at least one DL CC.

The various blocks shown in Figures 6 and 7 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s).

A first exemplary embodiment provides a method to determine and recover from broken DL CC for unlicensed band LTE systems. The method includes determining (e.g., by a processor), at a mobile device, whether a first DL CC on an unlicensed band is broken. The method includes, in response to determining that the first DL CC is broken, selecting (e.g., by a processor) an UL CC on the unlicensed band based at least in part on the first DL CC and transmitting (e.g., by a transmitter), from the mobile device on the UL CC, a message including an indication that the first DL CC is broken.

In a further exemplary embodiment of the method above, determining whether the first DL CC is broken includes, in response to receiving a first signal on the first DL CC, initiating a first timer; and, in response to no additional signals being successfully received on the first DL CC before the timer elapses, determining that the first DL CC is broken.

In another exemplary embodiment of any one of the methods above, the method also includes determining that at least one other DL CC on the unlicensed band is broken. The message also includes an indication that the at least one other DL CC is broken.

In a further exemplary embodiment of any one of the methods above, selecting the UL CC includes, in response to the first DL CC being a PCC, selecting an UL CC for transmitting of the message on a PUCCH,

In another exemplary embodiment of any one of the methods above, selecting the UL CC includes, in response to the first DL CC being a SCC, selecting an UL CC for transmitting of the message on a PUCCH.

In a further exemplary embodiment of any one of the methods above, the method also includes receiving recovery information. The recovery information may include parameters for at least one DL CC.

Another exemplary embodiment provides a method to determine and recover from broken DL CC for unlicensed band LTE systems. The method includes receiving (e.g., by a receiver), at an access node on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken. The method also includes, in response to receiving the message, selecting (e.g., by a processor) at least one DL CC on the unlicensed band and transmitting (e.g., by a transmitter) recovery information from the access node on the at least one DL CC.

In a further exemplary embodiment of the method above, the message also includes an indication that at least one other DL CC is broken.

In another exemplary embodiment of any one of the methods above, the recovery information includes parameters for at least one DL CC. The parameters may include: an ON-OFF pattern for the at least one DL CC, ARFCH of the at least one DL CC, a bitmap indicating broken CC and/or timer values.

In a further exemplary embodiment of any one of the methods above, transmitting the recovery information includes retransmitting the recovery information with a periodicity.

In another exemplary embodiment of any one of the methods above, the method also includes determining whether the first DL CC is broken for at least one additional UE. In a further exemplary embodiment of any one of the methods above, selecting the at least one DL CC includes selecting a DL CC transmitting a P-BCH.

In another exemplary embodiment of any one of the methods above, selecting the at least one DL CC includes selecting a DL CC transmitting a PDSCH,

A further exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes a processor and memory storing computer program code. The memory and the computer program code are configured to, with the processor, cause the apparatus to perform actions. The actions include to determine, at a mobile device, whether a first DL CC on an unlicensed band is broken, The actions also include, in response to determining that the first DL CC is broken, to select an UL CC on the unlicensed band based at least in part on the first DL CC and to transmit, from the mobile device on the UL CC, a message including an indication that the first DL CC is broken.

In another exemplary embodiment of the apparatus above, determining whether the first DL CC is broken includes, in response to receiving a first signal on the first DL CC, initiating a first timer; and, in response to no additional signals being successfully received on the first DL CC before the timer elapses, determining that the first DL CC is broken.

In a further exemplary embodiment of any one of the apparatus above, the actions also include to determine that at least one other DL CC on the unlicensed band is broken. The message also includes an indication that the at least one other DL CC is broken. In another exemplary embodiment of any one of the apparatus above, selecting the UL CC includes, in response to the first DL CC being a PCC, selecting an UL CC for transmitting of the message on a PUCCH.

In a further exemplary embodiment of any one of the apparatus above, selecting the UL CC includes, in response to the first DL CC being a SCC, selecting an UL CC for transmitting of the message on a PUCCH.

In another exemplary embodiment of any one of the apparatus above, the actions also include to receive recovery information. The recovery information may include parameters for at least one DL CC.

In a further exemplary embodiment of any one of the apparatus above, the apparatus is embodied in a mobile device.

In another exemplary embodiment of any one of the apparatus above, the apparatus is embodied in an integrated circuit.

A further exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes a processor and memory storing computer program code. The memory and the computer program code are configured to, with the processor, cause the apparatus to perform actions. The actions include to receive, at an access node on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken. The actions also include, in response to receiving the message, to select at least one DL CC on the unlicensed band and transmitting recovery information from the access node on the at least one DL CC.

In another exemplary embodiment of the apparatus above, the message also includes an indication that at least one other DL CC is broken.

In a further exemplary embodiment of any one of the apparatus above, the recovery information includes parameters for at least one DL CC. The parameters may include: an ON-OFF pattern for the at least one DL CC, ARFCH of the at least one DL CC, a bitmap indicating broken CC and/or timer values.

In another exemplary embodiment of any one of the apparatus above, transmitting the recovery information includes retransmitting the recovery information with a periodicity.

In a further exemplary embodiment of any one of the apparatus above, the actions also include to determine whether the first DL CC is broken for at least one additional UE.

In another exemplary embodiment of any one of the apparatus above, selecting the at least one DL CC includes selecting a DL CC transmitting a P-BCH.

In a further exemplary embodiment of any one of the apparatus above, selecting the at least one DL CC includes selecting a DL CC transmitting a PDSCH.

In another exemplary embodiment of any one of the apparatus above, the apparatus is embodied in a mobile device.

In a further exemplary embodiment of any one of the apparatus above, the apparatus is embodied in an integrated circuit.

Another exemplary embodiment provides a computer readable medium to determine and recover from broken DL CC for unlicensed band LTE systems. The computer readable medium is tangibly encoded with a computer program executable by a processor to perform actions. The actions include determining, at a mobile device, whether a first DL CC on an unlicensed band is broken. The actions also include, in response to determining that the first DL CC is broken, selecting an UL CC on the unlicensed band based at least in part on the first DL CC and transmitting, from the mobile device on the UL CC, a message including an indication that the first DL CC is broken.

In a further exemplary embodiment of the computer readable medium above, determining whether the first DL CC is broken includes, in response to receiving a first signal on the first DL CC, initiating a first timer; and, in response to no additional signals being successfully received on the first DL CC before the timer elapses, determining that the first DL CC is broken.

In another exemplary embodiment of any one of the computer readable media above, the actions also include determining that at least one other DL CC on the unlicensed band is broken. The message also includes an indication that the at least one other DL CC is broken.

In a further exemplary embodiment of any one of the computer readable media above, selecting the UL CC includes, in response to the first DL CC being a PCC, selecting an UL CC for transmitting of the message on a PUCCH.

In another exemplary embodiment of any one of the computer readable media above, selecting the UL CC includes, in response to the first DL CC being a SCC, selecting an UL CC for transmitting of the message on a PUCCH.

In a further exemplary embodiment of any one of the computer readable media above, the actions also include receiving recovery information. The recovery information may include parameters for at least one DL CC.

In another exemplary embodiment of any one of the computer readable media above, the computer readable medium is a non-transitory computer readable medium (e.g., CD-ROM, RAM, flash memory, etc.).

A further exemplary embodiment provides a computer readable medium to determine and recover from broken DL CC for unlicensed band LTE systems. The computer readable medium is tangibly encoded with a computer program executable by a processor to perform actions. The actions include receiving, at an access node on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken. The actions also include, in response to receiving the message, selecting at least one DL CC on the unlicensed band and transmitting recovery information from the access node on the at least one DL CC.

In another exemplary embodiment of the computer readable medium above, the message also includes an indication that at least one other DL CC is broken.

In a further exemplary embodiment of any one of the computer readable media above, the recovery information includes parameters for at least one DL CC. The parameters may include: an ON-OFF pattern for the at least one DL CC, ARFCH of the at least one DL CC, a bitmap indicating broken CC and/or timer values.

In another exemplary embodiment of any one of the computer readable media above, transmitting the recovery information includes retransmitting the recovery information with a periodicity.

In a further exemplary embodiment of any one of the computer readable media above, the actions also include determining whether the first DL CC is broken for at least one additional UE.

In another exemplary embodiment of any one of the computer readable media above, selecting the at least one DL CC includes selecting a DL CC transmitting a P-BCH.

In a further exemplary embodiment of any one of the computer readable media above, selecting the at least one DL CC includes selecting a DL CC transmitting a PDSCH.

A further exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes means for determining (e.g., a processor), at a mobile device, whether a first DL CC on an unlicensed band is broken. The apparatus includes means for selecting (e.g., a processor) an UL CC on the unlicensed band based at least in part on the first DL CC in response to determining that the first DL CC is broken and means for transmitting (e.g., a transmitter), from the mobile device on the UL CC, a message including an indication that the first DL CC is broken.

In another exemplary embodiment of the apparatus above, the determining means includes means for initiating a first timer in response to receiving a first signal on the first DL CC; and means for determining that the first DL CC is broken in response to no additional signals being successfully received on the first DL CC before the timer elapses.

In a further exemplary embodiment of any one of the apparatus above, the apparatus also includes means for determining that at least one other DL CC on the unlicensed band is broken. The message also includes an indication that the at least one other DL CC is broken.

In another exemplary embodiment of any one of the apparatus above, the selecting means includes means for selecting an UL CC for transmitting of the message on a PUCCH in response to the first DL CC being a PCC.

In a further exemplary embodiment of any one of the apparatus above, the selecting means includes means for selecting an UL CC for transmitting of the message on a PUCCH in response to the first DL CC being a SCC.

In another exemplary embodiment of any one of the apparatus above, the apparatus also includes means for receiving recovery information. The recovery information may include parameters for at least one DL CC. A further exemplary embodiment provides an apparatus to determine and recover from broken DL CC for unlicensed band LTE systems. The apparatus includes means for receiving (e.g., a receiver), at an access node on an UL CC on an unlicensed band, a message including an indication that a first DL CC on the unlicensed band is broken, The apparatus also includes means for selecting (e.g., a processor) at least one DL CC on the unlicensed band in response to receiving the message and means for transmitting (e.g., a transmitter) recovery information from the access node on the at least one DL CC.

In another exemplary embodiment of any one of the apparatus above, the transmitting means includes means for retransmitting the recovery information with a periodicity.

In a further exemplary embodiment of any one of the apparatus above, the apparatus also includes means for determining whether the first DL CC is broken for at least one additional UE,

In another exemplary embodiment of any one of the apparatus above, the selecting means includes means for selecting a DL CC transmitting a P-BCH.

In a further exemplary embodiment of any one of the apparatus above, the selecting means includes means for selecting a DL CC transmitting a PDSCH.

In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although not limited thereto. While various aspects of the exemplary embodiments may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as nonlimiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

It should thus be appreciated that at least some aspects of the exemplary embodiments may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments.

Various modifications and adaptations to the foregoing exemplary embodiments may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments.

For example, while the exemplary embodiments have been described above in the context of the E-UT AN (UTRAN-LTE) system, it should be appreciated that the exemplary embodiments are not limited for use with only this one particular type of wireless communication system, and that they may be used to advantage in other wireless communication systems such as for example (WLAN, UTRAN, GSM as appropriate). It should be noted that the terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples. Further, the various names used for the described parameters (e.g., C-RNTI, MID, etc.) are not intended to be limiting in any respect, as these parameters may be identified by any suitable names. Further, the formulas and expressions that use these various parameters may differ from those expressly disclosed herein. Further, the various names assigned to different channels (e.g., PUCCH, PDCCH, etc.) are not intended to be limiting in any respect, as these various channels may be identified by any suitable names.

Furthermore, some of the features of the various non-limiting and exemplary embodiments may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments, and not in limitation thereof.

Claims

What is claimed is:

1. A method comprising:

determining, at a mobile device, whether a first downlink component carrier on an unlicensed band is broken;

in response to determining that the first downlink component carrier is broken, selecting an uplink component carrier on the unlicensed band based at least in part on the first downlink component carrier and transmitting, from the mobile device on the uplink component carrier, a message comprising an indication that the first downlink component carrier is broken.

2. The method of claim 1 , where determining whether the first downlink component carrier is broken comprises:

in response to receiving a first signal on the first downlink component carrier, initiating a first timer; and

in response to no additional signals being successfully received on the first downlink component carrier before the timer elapses, determining that the first downlink component carrier is broken. 3. The method of any one of claims 1-2, further comprising determining that at least one other downlink component carrier on the unlicensed band is broken, where the message further comprises an indication that the at least one other downlink component carrier is broken. 4. The method of any one of claims 1-3, where selecting the uplink component carrier comprises, in response to the first downlink component carrier being a primary component carrier, selecting an uplink component carrier for transmitting of the message on a physical uplink control channel. 5. The method of any one of claims 1-3, where selecting the uplink component carrier comprises, in response to the first downlink component carrier being a secondary component carrier, selecting an uplink component carrier for transmitting of the message on a physical uplink control channel.

6. The method of any one of claims 1-5, further comprising receiving recovery information,

7. The method of claim 6, where the recovery information comprises parameters for at least one downlink component carrier. 8, A method comprising:

receiving, at an access node on an uplink component carrier on an unlicensed band, a message comprising an indication that a first downlink component carrier on the unlicensed band is broken;

in response to receiving the message, selecting at least one downlink component earner on the unlicensed band and transmitting recovery information from the access node on the at least one downlink component carrier.

9. The method of claim 8, where the message further comprises an indication that at least one other downlink component carrier is broken.

10. The method of any one of claims 8-9, where the recovery information comprises parameters for at least one downlink component carrier.

1 1. The method of claim 10, where the parameters comprise at least one of: an ON-OFF pattern for the at least one downlink component carrier, absolute radio frequency channel of the at least one downlink component carrier, a bitmap indicating broken component carrier, and timer values.

12. The method of any one of claims 8-11, where transmitting the recovery information comprises retransmitting the recovery information with a periodicity,

13. The method of any one of claims 8-12, further comprising determining whether the first downlink component carrier is broken for at least one additional mobile device.

14. The method of any one of claims 8-13, where selecting the at least one downlink component carrier comprises selecting a downlink component carrier transmitting a physical broadcast channel.

15. The method of any one of claims 8-13, where selecting the at least one downlink component carrier comprises selecting a downlink component carrier transmitting a physical downlink shared channel. 6. An apparatus, comprising a processor; and a memory storing computer program code, the memory and the computer program code configured to, with the processor, cause the apparatus to perform at least the following:

to determine, at a mobile device, whether a first downlink component carrier on an unlicensed band is broken;

in response to determining that the first downlink component carrier is broken, to select an uplink component carrier on the unlicensed band based at least in part on the first downlink component carrier and to transmit, from the mobile device on the uplink component carrier, a message comprising an indication that the first downlink component carrier is broken.

17. The apparatus of claim 16, where, when determining whether the first downlink component carrier is broken, the memory and the computer program code are further configured to cause the apparatus;

in response to receiving a first signal on the first downlink component carrier, to initiate a first timer; and

in response to no additional signals being successfully received on the first downlink component carrier before the timer elapses, to determine that the first downlink component carrier is broken.

18. The apparatus of any one of claims 16-17, where the memory and the computer program code are further configured to cause the apparatus to determine that at least one other downlink component carrier on the unlicensed band is broken, where the message further comprises an indication that the at least one other downlink component carrier is broken.

19. The apparatus of any one of claims 16-18, where, when selecting the uplink component carrier, the memory and the computer program code are further configured to cause the apparatus, in response to the first downlink component carrier being a primary component carrier, to select an uplink component carrier for transmitting of the message on a physical uplink control channel.

20. The apparatus of any one of claims 16-18, where, when selecting the uplink component carrier, the memory and the computer program code are further configured to cause the apparatus, in response to the first downlink component carrier being a secondary component carrier, to select an uplink component carrier for transmitting of the message on a physical uplink control channel.

21. The apparatus of any one of claims 16-20, where the memory and the computer program code are further configured to cause the apparatus to receive recovery information.

22. The apparatus of claim 21, where the recovery information comprises parameters for at least one downlink component carrier.

23. An apparatus, comprising a processor; and a memory storing computer program code, the memory and the computer program code configured to, with the processor, cause the apparatus to perform at least the following:

to receive, at an access node on an uplink component carrier on an unlicensed band, a message comprising an indication that a first downlink component carrier on the unlicensed band is broken; in response to receiving the message, to select at least one downlink component carrier on the unlicensed band and to transmit recovery information from the access node on the at least one downlink component carrier. 24. The apparatus of claim 23, where the message further comprises an indication that at least one other downlink component carrier is broken.

25. The apparatus of any one of claims 23-24, where the recovery information comprises parameters for at least one downlink component carrier.

26. The apparatus of claim 25, where the parameters comprise at least one of: an ON-OFF pattern for the at least one downlink component carrier, absolute radio frequency channel of the at least one downlink component carrier, a bitmap indicating broken component carrier, and timer values.

27. The apparatus of any one of claims 23-26, where, when transmitting the recovery information, the memory and the computer program code are further configured to cause the apparatus to retransmit the recovery information with a periodicity.

28. The apparatus of any one of claims 23-27, where the memory and the computer program code are further configured to cause the apparatus to determine whether the first downlink component carrier is broken for at least one additional mobile device. 29. The apparatus of any one of claims 23-28, where, when selecting the at least one downlink component carrier, the memory and the computer program code are further configured to cause the apparatus to select a downlink component carrier transmitting a physical broadcast channel. 30. The apparatus of any one of claims 23-28, where, when selecting the at least one downlink component carrier, the memory and the computer program code are further configured to cause the apparatus to select a downlink component carrier transmitting a physical downlink shared channel,

31. A computer readable medium tangibly encoded with a computer program executable by a processor to perform actions comprising:

32. The computer readable medium of claim 31, where determining whether the first downlink component carrier is broken comprises:

in response to no additional signals being successfully received on the first downlink component carrier before the timer elapses, determining that the first downlink component carrier is broken.

33. The computer readable medium of any one of claims 31-32, where the actions further comprise determining that at least one other downlink component carrier on the unlicensed band is broken and the message further comprises an indication that the at least one other downlink component carrier is broken.

34. The computer readable medium of any one of claims 31-33, where selecting the uplink component carrier comprises, in response to the first downlink component carrier being a primary component carrier, selecting an uplink component carrier for transmitting of the message on a physical uplink control channel.

35. The computer readable medium of any one of claims 31-33, where selecting the uplink component carrier comprises, in response to the first downlink component carrier being a secondary component carrier, selecting an uplink component carrier for transmitting of the message on a physical uplink control channel,

36. The computer readable medium of any one of claims 31-35, where the actions further comprise receiving recovery information.

37. The computer readable medium of claim 36, where the recovery information comprises parameters for at least one downlink component carrier.

38. A computer readable medium tangibly encoded with a computer program executable by a processor to perform actions comprising:

in response to receiving the message, selecting at least one downlink component carrier on the unlicensed band and transmitting recovery information from the access node on the at least one downlink component carrier.

39. The computer readable medium of claim 38, where the message further comprises an indication that at least one other downlink component carrier is broken,

40. The computer readable medium of any one of claims 38-39, where the recovery information comprises parameters for at least one downlink component carrier.

41. The computer readable medium of claim 40, where the parameters comprise at least one of: an ON-OFF pattern for the at least one downlink component carrier, absolute radio frequency channel of the at least one downlink component carrier, a bitmap indicating broken component carrier, and timer values.

42. The computer readable medium of any one of claims 38-41 , where transmitting the recovery information comprises retransmitting the recovery information with a periodicity. 43. The computer readable medium of any one of claims 38-42, where the actions further comprise determining whether the first downlink component carrier is broken for at least one additional mobile device.

44. The computer readable medium of any one of claims 38-43, where selecting the at least one downlink component carrier comprises selecting a downlink component carrier transmitting a physical broadcast channel.

45. The computer readable medium of any one of claims 38-43, where selecting the at least one downlink component carrier comprises selecting a downlink component carrier transmitting a physical downlink shared channel.

46. An apparatus comprising:

means for determining, at a mobile device, whether a first downlink component carrier on an unlicensed band is broken;

means for selecting an uplink component carrier on the unlicensed band based at least in part on the first downlink component carrier in response to determining that the first downlink component carrier is broken; and

means for transmitting, from the mobile device on the uplink component carrier, a message comprising an indication that the first downlink component carrier is broken.

47. The apparatus of claim 46, where the determining means comprises:

means for initiating a first timer in response to receiving a first signal on the first downlink component carrier; and

means for determining that the first downlink component carrier is broken in response to no additional signals being successfully received on the first downlink component carrier before the timer elapses.

48. The apparatus of any one of claims 46-47, further comprising means for determining that at least one other downlink component carrier on the unlicensed band is broken, where the message further comprises an indication that the at least one other downlink component carrier is broken.

49. The apparatus of any one of claims 46-48, where the selecting means comprises means for selecting an uplink component carrier for transmitting of the message on a physical uplink control channel in response to the first downlink component carrier being a primary component carrier.

50. The apparatus of any one of claims 46-48, where the selecting means comprises means for selecting an uplink component carrier for transmitting of the message on a physical uplink control channel in response to the first downlink component carrier being a secondary component carrier.

51. The apparatus of any one of claims 46-50, further comprising means for receiving recovery information. 52. The apparatus of claim 51, where the recovery information comprises parameters for at least one downlink component carrier.

53. An apparatus comprising:

means for receiving, at an access node on an uplink component carrier on an unlicensed band, a message comprising an indication that a first downlink component carrier on the unlicensed band is broken;

means for selecting at least one downlink component carrier on the unlicensed band in response to receiving the message; and

means for transmitting recovery information from the access node on the at least one downlink component carrier,

54. The apparatus of claim 53, where the message further comprises an indication that at least one other downlink component carrier is broken.

55. The apparatus of any one of claims 53-54, where the recovery information comprises parameters for at least one downlink component carrier.

56. The apparatus of claim 55, where the parameters comprise at least one of: an ON-OFF pattern for the at least one downlink component carrier, absolute radio frequency channel of the at least one downlink component carrier, a bitmap indicating broken component carrier, and timer values.

57. The apparatus of any one of claims 53-56, where the transmitting means comprises means for retransmitting the recovery information with a periodicity. 58. The apparatus of any one of claims 53-57, further comprising means for determining whether the first downlink component carrier is broken for at least one additional mobile device.

59. The apparatus of any one of claims 53-58, where the selecting means comprises means for selecting a downlink component carrier transmitting a physical broadcast channel.

60. The apparatus of any one of claims 53-58, where the selecting means comprises means for selecting a downlink component carrier transmitting a physical downlink shared.