LOW BANDWIDTH MACHINE TYPE COMMUNICATION IN A LONG TERM EVOLUTION NETWORK
20230217224 · 2023-07-06
Inventors
- Satish Nanjunda Swamy Jamadagni (Bangalore, IN)
- Sarvesha Anegundi Ganapathi (Bangalore, IN)
- Pradeep Krishnamurthy Hirisave (Bangalore, IN)
- Jinesh Parameshwaran Nair (Bangalore, IN)
Cpc classification
H04L5/0053
ELECTRICITY
H04L5/0044
ELECTRICITY
H04W72/0453
ELECTRICITY
H04W4/70
ELECTRICITY
International classification
H04W4/70
ELECTRICITY
H04W72/0453
ELECTRICITY
Abstract
The present invention provides a method and system for enabling machine type communication in a long term evolution (LTE) network environment. In one embodiment, a Physical (PHY) layer of an LTE protocol stack maps data bits in resource elements of a logical channel to resource elements of a physical channel. The PHY layer identifies the data bits intended for legacy devices but mapped to a first set of resource elements of machine type communication (MTC) devices and the data bits intended for the MTC device but mapped to the second set of resource elements of the legacy devices. Accordingly, the PHY layer remaps the data bits intended for the legacy devices to the second set of resource elements and the data bits intended for the MTC devices to the first set of resource elements prior to transmission.
Claims
1. A method performed by a terminal in a wireless communication system, the method comprising: receiving, from a base station, a master information block (MIB) including first information for identifying a common control region in which a physical downlink control channel (PDCCH) is to be received; and receiving, from the base station, a system information message including second information for identifying a common search space, wherein a frequency region of the common control region is within a bandwidth of a cell and includes consecutive physical resource blocks (PRBs), and wherein a time region of the common control region is within three orthogonal frequency division multiplexing (OFDM) symbols.
2. The method of claim 1, wherein a quadrature phase shift keying (QPSK) modulation scheme is applied for the common control region.
3. The method of claim 1, wherein the PDCCH is for scheduling the system information message.
4. The method of claim 1, wherein the system information message further includes third information for identifying a random access channel (RACH) region.
5. The method of claim 4, further comprising: transmitting, to the base station, a signal on the RACH region; and receiving, from the base station, a message for configuring one or more bandwidths in the bandwidth of the cell.
6. A method performed by a base station in a wireless communication system, the method comprising: transmitting, to a terminal, a master information block (MIB) including first information for identifying a common control region in which a physical downlink control channel (PDCCH) is to be transmitted; and transmitting, to the terminal, a system information message including second information for identifying a common search space, wherein a frequency region of the common control region is within a bandwidth of a cell and includes consecutive physical resource blocks (PRBs), and wherein a time region of the common control region is within three orthogonal frequency division multiplexing (OFDM) symbols.
7. The method of claim 6, wherein a quadrature phase shift keying (QPSK) modulation scheme is applied for the common control region.
8. The method of claim 6, wherein the PDCCH is for scheduling the system information message.
9. The method of claim 6, wherein the system information message further includes third information for identifying a random access channel (RACH) region.
10. The method of claim 9, further comprising: receiving, from the terminal, a signal on the RACH region; and transmitting, to the terminal, a message for configuring one or more bandwidths in the bandwidth of the cell.
11. A terminal in a wireless communication system, the terminal comprising: a transceiver; and a controller coupled with the transceiver and configured to: receive, from a base station, a master information block (MIB) including first information for identifying a common control region in which a physical downlink control channel (PDCCH) is to be received, and receive, from the base station, a system information message including second information for identifying a common search space, wherein a frequency region of the common control region is within a bandwidth of a cell and includes consecutive physical resource blocks (PRBs), and wherein a time region of the common control region is within three orthogonal frequency division multiplexing (OFDM) symbols.
12. The terminal of claim 11, wherein a quadrature phase shift keying (QPSK) modulation scheme is applied for the common control region.
13. The terminal of claim 11, wherein the PDCCH is for scheduling the system information message.
14. The terminal of claim 11, wherein the system information message further includes third information for identifying a random access channel (RACH) region.
15. The terminal of claim 14, wherein the controller is further configured to: transmit, to the base station, a signal on the RACH region, and receive, from the base station, a message for configuring one or more bandwidths in the bandwidth of the cell.
16. A base station in a wireless communication system, the base station comprising: a transceiver; and a controller coupled with the transceiver and configured to: transmit, to a terminal, a master information block (MIB) including first information for identifying a common control region in which a physical downlink control channel (PDCCH) is to be transmitted, and transmit, to the terminal, a system information message including second information for identifying a common search space, wherein a frequency region of the common control region is within a bandwidth of a cell and includes consecutive physical resource blocks (PRBs), and wherein a time region of the common control region is within three orthogonal frequency division multiplexing (OFDM) symbols.
17. The base station of claim 16, wherein a quadrature phase shift keying (QPSK) modulation scheme is applied for the common control region.
18. The base station of claim 16, wherein the PDCCH is for scheduling the system information message.
19. The base station of claim 16, wherein the system information message further includes third information for identifying a random access channel (RACH) region.
20. The base station of claim 19, wherein the controller is further configured to: receive, from the terminal, a signal on the RACH region, and transmit, to the terminal, a message for configuring one or more bandwidths in the bandwidth of the cell.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0009]
[0010]
[0011]
[0012]
[0013]
[0014]
[0015]
[0016]
[0017]
[0018]
[0019]
[0020] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
DETAILED DESCRIPTION
[0021] The present invention provides a method and system for enabling machine type communication over a narrow frequency region within a larger bandwidth cell. In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
[0022]
[0023] Each of the MTC devices 104A-N includes a low cost LTE modem 112 configured for operating in narrow bandwidth of 1.25 mega-Hertz (MHz). The network entity 102 may comprise a base station in an LTE network, sometimes referred to as an Evolved Node B (eNodeB). The network entity 102 includes an LTE protocol stack 108. The LTE protocol stack 108 is a layered protocol stack. Each layer of the protocol stack 108 represents a set of protocols or functions needed to communicate over the network 110.
[0024] Referring to
[0025] User plane data in the form of IP packets to be transmitted enters the PDCP layer 202 where the IP headers may be compressed to reduce the number of bits transmitted over the air interface. The PDCP layer 202 also performs ciphering and deciphering of the IP packets for security. The RLC layer 204 ensures almost error free, in-sequence delivery of compressed IP packets to a PDCP layer at the receiving terminal, which is needed for certain types of communication. At the transmitting terminal, the RLC layer 204 segments and/or concatenates compressed IP packets received over radio bearers from the PDCP layer 202 to create RLC protocol data units (PDUs).
[0026] The MAC layer 206 maps RLC PDUs received from the RLC layer 204 on various logical channels to corresponding transport channels (also referred to as physical channels). The MAC layer 206 is also responsible for uplink and downlink scheduling. The MAC PDUs are fed by the MAC layer 206 to the PHY layer 208. The PHY layer 208 handles coding/decoding, modulation/demodulation, interleaving, and mapping of data bits prior to transmission of one or more PHY layer PDUs.
[0027] According to one embodiment, the network entity 102 allocates a radio access channel (RACH) region in a frequency region dedicated for low bandwidth MTC devices (herein after referred to as ‘1.25 MHz frequency region’) to the MTC devices 104A-N. Then, the network entity 102 transmits a MTC specific information message indicating the allocated RACH region and a common search space to the MTC devices 104A-N. In response, the MTC devices 104A-N send a RACH message on the RACH region in the 1.25 MHz frequency region. As a consequence, the network entity 102 establishes a Radio Resource Connection with the MTC device 104A and configures a dedicated search space for the MTC devices 104A-N upon successful establishment of the radio resource connection. Furthermore, the network entity 102 allocates resources for the MTC devices 104A-N within the 1.25 MHz frequency region and indicates the resources allocated within the 1.25 MHz frequency region to the MTC devices 104A-N.
[0028] Prior to transmission of data, the PHY layer 208 maps the interleaved data bits intended for the MTC devices 104A-N to respective resource elements of a physical channel(s) belonging to 1.25 MHz frequency region in a 20 MHz frequency band. The PHY layer 208 also maps the interleaved data bits intended for the legacy devices 106A-N to respective resource elements of the physical channel belonging to a frequency region outside the 1.25 MHz frequency region and within the 20 MHz frequency band. Accordingly, the eNodeB 102 transmits the data bits mapped to the respective resource elements over a radio frequency corresponding to the 1.25 MHz frequency region and the region outside the 1.25 MHz frequency region to the MTC devices 104A-N and the legacy devices 106A-N respectively.
[0029]
[0030]
[0031]
[0032] At step 406, the MTC device 104A sends a RACH message on the RACH region in the 1.25 MHz frequency region. At step 408, the network entity 104A establishes a Radio Resource Connection with the MTC device 104A. At step 410, the network entity 102 configures a dedicated search space for the MTC device 104A upon successful establishment of the radio resource connection as shown in
[0033] At step 412, the network entity 102 allocates resources for the MTC device 104A within the 1.25 MHz frequency region. For example, the resources may include resource elements in the physical channel falling within the 1.25 MHz frequency region. In one embodiment, resource elements in an entire radio frame falling within the 1.25 MHz frequency region are allocated to the MTC device 104A and resource elements falling outside the 1.25 MHz frequency region but falling within 20 MHz frequency band are allocated to legacy devices 106A-N as shown in
[0034] In another embodiment, resource elements in one of subframes of a radio frame are allocated exclusively for low bandwidth MTC devices 104A-N while the resource elements in remaining subframes of the radio frame are allocated to the legacy devices 106A-N as illustrated in
[0035] At step 414, the network entity 102 sends resources allocated within the 1.25 MHz frequency region to the MTC device 104A. For example, the allocation of the MTC scheduling region is indicated to the MTC devices 104A-N in a master information block message or a system information block message.
[0036]
[0037] At step 506, the data bits in resource elements of a logical channel are mapped to resource elements of a physical channel. It can be noted that, the physical channel contains a first set resource elements which belong to 1.25 MHz frequency region and a second set of resource elements which belong to a region outside 1.25 MHz within a 20 MHz frequency band. For example, the data bits in the resource elements of the physical channel:
where n.sub.VRB is obtained from scheduling grant. The parameter pusch-Hopping Offset (N.sub.RB.sup.HO) is provided by the MAC layer 206. The size N.sub.RB.sup.sb of each sub-band is given by:
where, the number of sub-bands N.sub.sb is given by the MAC layer 206. The function ƒ.sub.m(i)∈{0,1} determines whether mirroring is used or not. The parameter Hopping-mode determines if hopping is “inter-subframe” or “intra and inter-subframe”.
The hopping function ƒ.sub.hop(i) and the function ƒ.sub.m (i) are given by:
where ƒ.sub.hop (−1)=0 and the pseudo-random sequence c(i) is given by section 7.2 and CURRENT_TX_NB indicates the transmission number for the transport block transmitted in slot n.sub.s. The pseudo-random sequence generator shall be initialised with c.sub.init=N.sub.ID.sup.cell for frame structure type 1 and c.sub.init=2.sup.9.Math.(n.sub.f mod 4)+N.sub.ID.sup.cell for frame structure type 2 at the start of each frame.
[0038] At step 508, the data bits intended for the legacy devices 106A-N but mapped to the first set of resource elements of the MTC devices 104A-N are identified. Similarly, at step 508, the data bits intended for the MTC device 104A-N but mapped to the second set of resource elements of the legacy devices 106A-N are identified. At step 510, the data bits intended for the legacy devices 106A-N are remapped to the second resource elements and the data bits intended for the MTC devices 104A-N are remapped to the first set of resource elements. In one embodiment, the eNodeB 102 remaps data bits intended for the legacy devices 106A-N to the resource elements outside the 1.25 MHz frequency region as follows:
If n.sub.prb1.25==n.sub.prb20,
n.sub.prb20=fn.sub.20(fn.sup.−1.sub.1.25(n.sub.prb1.25))
where, n.sub.prb1.25 is Physical Resource Block (PRB) for 1.25 MHz frequency region calculated using the conventional formula, fn.sub.20 is the conventional formula for 20 MHz frequency band, and fn.sup.−1.sub.1.25 is the reverse conventional formula (i.e., the reverse mapping from the physical channel to logical channels).
[0039] At step 512, the data bits mapped to the respective resource elements are transmitted over a radio frequency corresponding to the 1.25 MHz frequency region and the region outside the 1.25 MHz frequency region to the MTC devices 104A-N and the legacy devices 106A-N respectively.
[0040]
[0041] Prior to transmitting the data bits 604A-J, the eNodeB 102 maps the modulated data bits 604A-J to the resource elements 608A-D, 610A-F of the physical channel 606. It can be seen that the data bits 604B and 604I are mapped to the resource elements 608A and 608C while the data bits 604D and 604F are mapped to the resource elements 610B and 610F. However, the data bits 604B and 604I should have been mapped to the resource elements 610B and 610F while the data bits 604D and 604F should have been mapped to the resource elements 608A and 608C. This is because, the data bits 604D and 604F are intended for the MTC devices 104A-N and should be transmitted over 1.25 MHz frequency region. Similarly, the data bits 604B and 604I are intended for the legacy devices 104A-N and should be transmitted over frequencies falling outside the 1.25 MHz frequency region.
[0042] In this scenario, the eNodeB 102 identifies wrongly mapped data bits (i.e., data bits 604B, 604D, 604F, and 604I) and remaps the data bits 604D and 604F to the resource elements 608A and 608C, and the data bits 604B and 604I to the resource elements 610B and 610F. Thus, the data bits 604D-G are correctly mapped to resource elements 608A-D belonging to the 1.25 MHz frequency region reserved for the MTC devices 104A-N.
[0043]
[0044] At step 706, data bits intended for the MTC devices 104A-N are mapped to resource elements in the MTC scheduling region of the subframe. At step 708, the data bits mapped to the resource elements are transmitted to the MTC devices 104A-N over a radio frequency corresponding to the MTC scheduling region.
[0045]
[0046]
[0047] At step 906, the data bits mapped to the respective resource elements of the logical channel are demodulated using an appropriate demodulation scheme. At step 908, the demodulated data bits mapped to the respective resource elements of the logical channel are decoded using an appropriate decoding technique and sent to the MAC layer 206 for further processing.
[0048] Apart from the embodiments described in
[0049] The present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Furthermore, the various devices, modules, and the like described herein may be enabled and operated using hardware circuitry, for example, complementary metal oxide semiconductor based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium. For example, the various electrical structure and methods may be embodied using transistors, logic gates, and electrical circuits, such as application specific integrated circuit.