US20070086405A1

US20070086405A1 - Method and apparatus of preprocessing for frequency domain signal processing

Info

Publication number: US20070086405A1
Application number: US11/536,519
Authority: US
Inventors: Shu Wang
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2005-09-28
Filing date: 2006-09-28
Publication date: 2007-04-19
Also published as: EP1929650A2; CN101366307A; CN101390298A; KR20080054410A; EP1929822A2; CN101390298B; WO2007037637A2; WO2007037639A3; WO2007037639A2; WO2007037637A3; KR20080066733A; KR20080053943A; WO2007037634A3; US20070072550A1; CN101313479A; US20070070945A1; WO2007037634A2; US7684523B2; EP1929651A2

Abstract

A method of transmitting at least one packet in a wireless mobile communication system is disclosed. More specifically, the method includes transmitting at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol.

Description

This application claims the benefit of U.S. Provisional Application No. 60/722,018, filed on Sep. 28, 2005, which is hereby incorporated by reference,

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method of signal processing, and more particularly, to a method and an apparatus of preprocessing for frequency domain signal processing.
2. Discussion of the Related Art
In the world of cellular telecommunications, those skilled in the art often use the terms 1G, 2G, and 3G. The terms refer to the generation of the cellular technology used. 1G refers to the first generation, 2G to the second generation, and 3G to the third generation.
1G refers to the analog phone system, known as an AMPS (Advanced Mobile Phone Service) phone systems. 2G is commonly used to refer to the digital cellular systems that are prevalent throughout the world, and include CDMAOne, Global System for Mobile communications (GSM), and Time Division Multiple Access (TDMA). 2G systems can support a greater number of users in a dense area than can 1G systems.
3G commonly refers to the digital cellular systems currently being deployed. These 3G communication systems are conceptually similar to each other with some significant differences.
Wireless communication systems are currently designed to provide high data rates at high terminal speeds. At the same time, the wireless communication systems seek to provide reliable transmission of information. One major obstacle associated with providing reliable information at high data rates is interference. More specifically, inter symbol interference (ISI) affect reliable transmission. Here, the ISI refers to the effect of neighboring symbols on the current symbol. Unless the ISI is handled properly, it can lead to high bit error rates (BER) in the recover of the transmitted sequence at the receiver. Consequently, various methods have been and still are being developed to reduce the effects of the ISI thus increasing the wireless communication system's performance.
Unreliable transmission can be caused by distorted signals through fading channels before the signals reach the receiving end. To provide more reliable transmission and minimize signal distortions due to the ISI, various signal processing schemes can be employed at the receiving end as wells as at the transmitting end.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method and an apparatus of preprocessing for frequency domain signal processing that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a method of transmitting at least one packet in a wireless mobile communication system.
Another object of the present invention is to provide a method of receiving at least one packet in a wireless mobile communication system.
A further object of the present invention is to provide a packet configured to transmit data from a transmitting end to a receiving end in a wireless communication system.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of transmitting at least one packet in a wireless mobile communication system includes transmitting at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol.
In another aspect of the present invention, a method of transmitting at least one packet in a wireless mobile communication system includes transmitting at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol. Here, the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each packet.
In a further aspect of the present invention, a method of receiving at least one packet in a wireless mobile communication system includes receiving at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol.
Yet, in another aspect of the present invention, a packet configured to transmit data from a transmitting end to a receiving end in a wireless communication system includes at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is placed between at least one pilot symbol and the at least one data symbol.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings;
FIG. 1 illustrates wireless communication network architecture;
FIG. 2A illustrates a CDMA spreading and de-spreading process;
FIG. 2B illustrates a CDMA spreading and de-spreading process using multiple spreading sequences;
FIG. 3 illustrates a data link protocol architecture layer for a cdma2000 wireless network;
FIG. 4 illustrates cdma2000 call processing;
FIG. 5 illustrates the cdma2000 initialization state;
FIG. 6 illustrates the cdma2000 system access state;
FIG. 7 illustrates a conventional cdma2000 access attempt;
FIG. 8 illustrates a conventional cdma2000 access sub-attempt;
FIG. 9 illustrates the conventional cdma2000 system access state using slot offset;
FIG. 10 illustrates a comparison of cdma2000 for 1× and 1×EV-DO;
FIG. 11 illustrates a network architecture layer for a 1×EV-DO wireless network;
FIG. 12 illustrates 1×EV-DO default protocol architecture;
FIG. 13 illustrates 1×EV-DO non-default protocol architecture;
FIG. 14 illustrates 1×EV-DO session establishment;
FIG. 15 illustrates 1×EV-DO connection layer protocols;
FIG. 16 illustrates a placement of a silent block/period relative to a pilot block and a data block at the transmitting end; and
FIG. 17 illustrates a placement of a silent block relative to a pilot block and a data block at the receiving end.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Referring to FIG. 1, a wireless communication network architecturel is illustrated. A subscriber uses a mobile station (MS) 2 to access network services. The MS 2 may be a portable communications unit, such as a hand-held cellular phone, a communication unit installed in a vehicle, or a fixed-location communications unit.
The electromagnetic waves for the MS 2 are transmitted by the Base Transceiver System (BTS) 3 also known as node B. The BTS 3 consists of radio devices such as antennas and equipment for transmitting and receiving radio waves. The BS 6 Controller (BSC) 4 receives the transmissions from one or more BTS's. The BSC 4 provides control and management of the radio transmissions from each BTS 3 by exchanging messages with the BTS and the Mobile Switching Center (MSC) 5 or Internal IP Network. The BTS's 3 and BSC 4 are part of the BS 6 (BS) 6.
The BS 6 exchanges messages with and transmits data to a Circuit Switched Core Network (CSCN) 7 and Packet Switched Core Network (PSCN) 8. The CSCN 7 provides traditional voice communications and the PSCN 8 provides Internet applications and multimedia services.
The Mobile Switching Center (MSC) 5 portion of the CSCN 7 provides switching for traditional voice communications to and from a MS 2 and may store information to support these capabilities. The MSC 2 may be connected to one of more BS's 6 as well as other public networks, for example a Public Switched Telephone Network (PSTN) (not shown) or Integrated Services Digital Network (ISDN) (not shown). A Visitor Location Register (VLR) 9 is used to retrieve information for handling voice communications to or from a visiting subscriber. The VLR 9 may be within the MSC 5 and may serve more than one MSC.
A user identity is assigned to the Home Location Register (HLR) 10 of the CSCN 7 for record purposes such as subscriber information, for example Electronic Serial Number (ESN), Mobile Directory Number (MDR), Profile Information, Current Location, and Authentication Period. The Authentication Center (AC) 11 manages authentication information related to the MS 2. The AC 11 may be within the HLR 10 and may serve more than one HLR. The interface between the MSC 5 and the HLR/ AC 10, 11 is an IS-41 standard interface 18.
The Packet data Serving Node (PDSN) 12 portion of the PSCN 8 provides routing for packet data traffic to and from MS 2. The PDSN 12 establishes, maintains, and terminates link layer sessions to the MS 2's 2 and may interface with one of more BS 6 and one of more PSCN 8.
The Authentication, Authorization and Accounting (AAA) 13 Server provides Internet Protocol authentication, authorization and accounting functions related to packet data traffic. The Home Agent (HA) 14 provides authentication of MS 2 IP registrations, redirects packet data to and from the Foreign Agent (FA) 15 component of the PDSN 8, and receives provisioning information for users from the AAA 13. The HA 14 may also establish, maintain, and terminate secure communications to the PDSN 12 and assign a dynamic IP address. The PDSN 12 communicates with the AAA 13, HA 14 and the Internet 16 via an Internal IP Network.
There are several types of multiple access schemes, specifically Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). In FDMA, user communications are separated by frequency, for example, by using 30 KHz channels. In TDMA, user communications are separated by frequency and time, for example, by using 30 KHz channels with 6 timeslots. In CDMA, user communications are separated by digital code.
In CDMA, All users on the same spectrum, for example, 1.25 MHz. Each user has a unique digital code identifier and the digital codes separate users to prevent interference.
A CDMA signal uses many chips to convey a single bit of information. Each user has a unique chip pattern, which is essentially a code channel. In order to recover a bit, a large number of chips are integrated according to a user's known chip pattern. Other user's code patterns appear random and are integrated in a self-canceling manner and, therefore, do not disturb the bit decoding decisions made according to the user's proper code pattern.
Input data is combined with a fast spreading sequence and transmitted as a spread data stream. A receiver uses the same spreading sequence to extract the original data. FIG. 2A illustrates the spreading and de-spreading process. As illustrated in FIG. 2B, multiple spreading sequences may be combined to create unique, robust channels.
A Walsh code is one type of spreading sequence. Each Walsh code is 64 chips long and is precisely orthogonal to all other Walsh codes. The codes are simple to generate and small enough to be stored in read only memory (ROM).
A short PN code is another type of spreading sequence. A short PN code consists of two PN sequences (I and Q), each of which is 32,768 chips long and is generated in similar, but differently tapped 15-bit shift registers. The two sequences scramble the information on the I and Q phase channels.
A long PN code is another type of spreading sequence. A long PN code is generated in a 42-bit register and is more than 40 days long, or about 4×10¹³chips long. Due to its length, a long PN code cannot be stored in ROM in a terminal and, therefore, is generated chip-by-chip.
Each MS 2 codes its signal with the PN long code and a unique offset, or public long code mask, computed using the long PN code ESN of 32-bits and 10 bits set by the system. The public long code mask produces a unique shift. Private long code masks may be used to enhance privacy. When integrated over as short a period as 64 chips, MS 2 with different long PN code offsets will appear practically orthogonal.
CDMA communication uses forward channels and reverse channels. A forward channel is utilized for signals from a BTS 3 to a MS 2 and a reverse channel is utilized for signals from a MS to a BTS.
A forward channel uses its specific assigned Walsh code and a specific PN offset for a sector, with one user able to have multiple channel types at the same time. A forward channel is identified by its CDMA RF carrier frequency, the unique short code PN offset of the sector and the unique Walsh code of the user. CDMA forward channels include a pilot channel, sync channel, paging channels and traffic channels.
The pilot channel is a “structural beacon” which does not contain a character stream, but rather is a timing sequence used for system acquisition and as a measurement device during handoffs. A pilot channel uses Walsh code 0.
The sync channel carries a data stream of system identification and parameter information used by MS 2 during system acquisition. A sync channel uses Walsh code 32.
There may be from one to seven paging channels according to capacity requirements. Paging channels carry pages, system parameter information and call setup orders. Paging channels use Walsh codes 1-7.
The traffic channels are assigned to individual users to carry call traffic. Traffic channels use any remaining Walsh codes subject to overall capacity as limited by noise.
A reverse channel is utilized for signals from a MS 2 to a BTS 3 and uses a Walsh code and offset of the long PN sequence specific to the MS, with one user able to transmit multiple types of channels simultaneously. A reverse channel is identified by its CDMA RF carrier frequency and the unique long code PN Offset of the individual MS 2. Reverse channels include traffic channels and access channels.
Individual users use traffic channels during actual calls to transmit traffic to the BTS 3. A reverse traffic channel is basically a user-specific public or private long code Mask and there are as many reverse traffic channels as there are CDMA terminals.
An MS 2 not yet involved in a call uses access channels to transmit registration requests, call setup requests, page responses, order responses and other signaling information. An access channel is basically a public long code offset unique to a BTS 3 sector. Access channels are paired with paging channels, with each paging channel having up to 32 access channels.
CDMA communication provides many advantages. Some of the advantages are variable rate vocoding and multiplexing, power control, use of RAKE receivers and soft handoff.
CDMA allows the use of variable rate vocoders to compress speech, reduce bit rate and greatly increase capacity. Variable rate vocoding provides full bit rate during speech, low data rates during speech pauses, increased capacity and natural sound. Multiplexing allows voice, signaling and user secondary data to be mixed in CDMA frames.
By utilizing forward power control, the BTS 3 continually reduces the strength of each user's forward baseband chip stream. When a particular MS 2 experiences errors on the forward link, more energy is requested and a quick boost of energy is supplied after which the energy is again reduced.
Using a RAKE receiver allows a MS 2 to use the combined outputs of the three traffic correlators, or “RAKE fingers,” every frame. Each RAKE finger can independently recover a particular PN Offset and Walsh code. The fingers may be targeted on delayed multipath reflections of different BTS's 3, with a searcher continuously checking pilot signals.
The MS 2 drives soft handoff. The MS 2 continuously checks available pilot signals and reports to the BTS 3 regarding the pilot signals it currently sees. The BTS 3 assigns up to a maximum of six sectors and the MS 2 assigns its fingers accordingly. All messages are sent by dim-and-burst without muting. Each end of the communication link chooses the best configuration on a frame-by-frame basis, with handoff transparent to users.
A cdma2000 system is a third-generation (3G) wideband; spread spectrum radio interface system that uses the enhanced service potential of CDMA technology to facilitate data capabilities, such as Internet and intranet access, multimedia applications, high-speed business transactions, and telemetry. The focus of cdma2000, as is that of other third-generation systems, is on network economy and radio transmission design to overcome the limitations of a finite amount of radio spectrum availability.
FIG. 3 illustrates a data link protocol architecture layer 20 for a cdma2000 wireless network. The data link protocol architecture layer 20 includes an Upper Layer 60, a Link Layer 30 and a Physical layer 21.
The Upper layer 60 includes three sublayers; a Data Services sublayer 61; a Voice Services sublayer 62 and a Signaling Services sublayer 63. Data services 61 are services that deliver any form of data on behalf of a mobile end user and include packet data applications such as IP service, circuit data applications such as asynchronous fax and B-ISDN emulation services, and SMS. Voice services 62 include PSTN access, mobile-to-mobile voice services, and Internet telephony. Signaling 63 controls all aspects of mobile operation.
The Signaling Services sublayer 63 processes all messages exchanged between the MS 2 and BS 6. These messages control such functions as call setup and teardown, handoffs, feature activation, system configuration, registration and authentication.
The Link Layer 30 is subdivided into the Link Access Control (LAC) sublayer 32 and the Medium Access Control (MAC) sublayer 31. The Link Layer 30 provides protocol support and control mechanisms for data transport services and performs the functions necessary to map the data transport needs of the Upper layer 60 into specific capabilities and characteristics of the Physical Layer 21. The Link Layer 30 may be viewed as an interface between the Upper Layer 60 and the Physical Layer 20.
The separation of MAC 31 and LAC 32 sublayers is motivated by the need to support a wide range of Upper Layer 60 services and the requirement to provide for high efficiency and low latency data services over a wide performance range, specifically from 1.2 Kbps to greater than 2 Mbps. Other motivators are the need for supporting high Quality of Service (QoS) delivery of circuit and packet data services, such as limitations on acceptable delays and/or data BER (bit error rate), and the growing demand for advanced multimedia services each service having a different QoS requirements.
The LAC sublayer 32 is required to provide a reliable, in-sequence delivery transmission control function over a point-to-point radio transmission link 42. The LAC sublayer 32 manages point-to point communication channels between upper layer 60 entities and provides framework to support a wide range of different end-to-end reliable Link Layer 30 protocols.
The Link Access Control (LAC) sublayer 32 provides correct delivery of signaling messages. Functions include assured delivery where acknowledgement is required, unassured delivery where no acknowledgement is required, duplicate message detection, address control to deliver a message to an individual MS 2, segmentation of messages into suitable sized fragments for transfer over the physical medium, reassembly and validation of received messages and global challenge authentication.
The MAC sublayer 31 facilitates complex multimedia, multi-services capabilities of 3G wireless systems with QoS management capabilities for each active service. The MAC sublayer 31 provides procedures for controlling the access of packet data and circuit data services to the Physical Layer 21, including the contention control between multiple services from a single user, as well as between competing users in the wireless system. The MAC sublayer 31 also performs mapping between logical channels and physical channels, multiplexes data from multiple sources onto single physical channels and provides for reasonably reliable transmission over the Radio Link Layer using a Radio Link Protocol (RLP) 33 for a best-effort level of reliability. Signaling Radio Burst Protocol (SRBP) 35 is an entity that provides connectionless protocol for signaling messages. Multiplexing and QoS Control 34 is responsible for enforcement of negotiated QoS levels by mediating conflicting requests from competing services and the appropriate prioritization of access requests.
The Physical Layer 20 is responsible for coding and modulation of data transmitted over the air. The Physical Layer 20 conditions digital data from the higher layers so that the data may be transmitted over a mobile radio channel reliably.
The Physical Layer 20 maps user data and signaling, which the MAC sublayer 31 delivers over multiple transport channels, into a physical channels and transmits the information over the radio interface. In the transmit direction, the functions performed by the Physical Layer 20 include channel coding, interleaving, scrambling, spreading and modulation. In the receive direction, the functions are reversed in order to recover the transmitted data at the receiver.
FIG. 4 illustrates an overview of call processing Processing a call includes pilot and sync channel processing, paging channel processing, access channel processing and traffic channel processing.
Pilot and sync channel processing refers to the MS 2 processing the pilot and sync channels to acquire and synchronize with the CDMA system in the MS 2 Initialization State. Paging channel processing refers to the MS 2 monitoring the paging channel or the forward common control channel (F-CCCH) to receive overhead and mobile-directed messages from the BS 6 in the Idle State. Access channel processing refers to the MS 2 sending messages to the BS 6 on the access channel or the Enhanced access channel in the System Access State, with the BS 6 always listening to these channels and responding to the MS on either a paging channel or the F-CCCH. Traffic channel processing refers to the BS 6 and MS 2 communicating using dedicated forward and reverse traffic channels in the MS 2 Control on Traffic Channel State, with the dedicated forward and reverse traffic channels carrying user information, such as voice and data.
FIG. 5 illustrates the initialization state of a MS 2. The Initialization state includes a System Determination Substate, Pilot Channel Acquisition, Sync Channel Acquisition, a Timing Change Substate and a Mobile Station Idle State.
System Determination is a process by which the MS 2 decides from which system to obtain service. The process could include decisions such as analog versus digital, cellular versus PCS, and A carrier versus B carrier. A custom selection process may control System Determination. A service provider using a redirection process may also control System determination. After the MS 2 selects a system, it must determine on which channel within that system to search for service. Generally the MS 2 uses a prioritized channel list to select the channel.
Pilot Channel Processing is a process whereby the MS 2 first gains information regarding system timing by searching for usable pilot signals. Pilot channels contain no information, but the MS 2 can align its own timing by correlating with the pilot channel. Once this correlation is completed, the MS 2 is synchronized with the sync channel and can read a sync channel message to further refine its timing. The MS 2 is permitted to search up to 15 seconds on a single pilot channel before it declares failure and returns to System Determination to select either another channel or another system. The searching procedure is not standardized, with the time to acquire the system depending on implementation.
In cdma2000, there may be many pilot channels, such as OTD pilot STS pilot and Auxiliary pilot, on a single channel. During System Acquisition, the MS 2 will not find any of these pilot channels because they are use different Walsh codes and the MS is only searching for Walsh 0.
The sync channel message is continuously transmitted on the sync channel and provides the MS 2 with the information to refine timing and read a paging channel. The mobile receives information from the BS 6 in the sync channel message that allows it to determine whether or not it will be able to communicate with that BS.
In the Idle State, the MS 2 receives one of the paging channels and processes the messages on that channel. Overhead or configuration messages are compared to stored sequence numbers to ensure the MS 2 has the most current parameters. Messages to the MS 2 are checked to determine the intended subscriber.
The BS 6 may support multiple paging channels and/or multiple CDMA channels (frequencies). The MS 2 uses a hash function based on its IMSI to determine which channel and frequency to monitor in the Idle State. The BS 6 uses the same hash function to determine which channel and frequency to use when paging the MS 2.
Using a Slot Cycle Index (SCI) on the paging channel and on F-CCCH supports slotted paging. The main purpose of slotted paging is to conserve battery power in MS 2. Both the MS 2 and BS 6 agree in which slots the MS will be paged. The MS 2 can power down some of its processing circuitry during unassigned slots. Either the General Page message or the Universal Page message may be used to page the mobile on F-CCCH. A Quick paging channel that allows the MS 2 to power up for a shorter period of time than is possible using only slotted paging on F-PCH or F-CCCH is also supported.
FIG. 6 illustrates the System Access state. The first step in the system access process is to update overhead information to ensure that the MS 2 is using the correct access channel parameters, such as initial power level and power step increments. A MS 2 randomly selects an access channel and transmits without coordination with the BS 6 or other MS. Such a random access procedure can result in collisions. Several steps can be taken to reduce the likelihood of collision, such as use of a slotted structure, use of a multiple access channel, transmitting at random start times and employing congestion control, for example, overload classes.
The MS 2 may send either a request or a response message on the access channel. A request is a message sent autonomously, such as an Origination message. A response is a message sent in response to a message received from the BS 6. For example, a Page Response message is a response to a General Page message or a Universal message.
An access attempt, which refers to the entire process of sending one Layer 2 encapsulated PDU and receiving an acknowledgment for the PDU, consists of one or more access sub-attempts, as illustrated in FIG. 7. An access sub-attempt includes of a collection of access probe sequences, as illustrated in FIG. 8. Sequences within an access sub-attempt are separated by a random backoff interval (RS) and a persistence delay (PD). PD only applies to access channel request, not response. FIG. 9 illustrates a System Access state in which collisions are avoided by using a slot offset of 0-511 slots.
The Multiplexing and QoS Control sublayer 34 has both a transmitting function and a receiving function, The transmitting function combines information from various sources, such as Data Services 61, Signaling Services 63 or Voice Services 62, and forms Physical layer SDUs and PDCHCF SDUs for transmission. The receiving function separates the information contained in Physical Layer 21 and PDCHCF SDUs and directs the information to the correct entity, such as Data Services 61, Upper Layer Signaling 63 or Voice Services 62.
The Multiplexing and QoS Control sublayer 34 operates in time synchronization with the Physical Layer 21. If the Physical Layer 21 is transmitting with a non-zero frame offset, the Multiplexing and QoS Control sublayer 34 delivers Physical Layer SDUs for transmission by the Physical Layer at the appropriate frame offset from system time.
The Multiplexing and QoS Control sublayer 34 delivers a Physical Layer 21 SDU to the Physical Layer using a physical-channel specific service interface set of primitives. The Physical Layer 21 delivers a Physical Layer SDU to the Multiplexing and QoS Control sublayer 34 using a physical channel specific Receive Indication service interface operation.
The SRBP Sublayer 35 includes the sync channel, forward common control channel, broadcast control channel, paging channel and access channel procedures.
The LAC Sublayer 32 provides services to Layer 3 60. SDUs are passed between Layer 3 60 and the LAC Sublayer 32. The LAC Sublayer 32 provides the proper encapsulation of the SDUs into LAC PDUs, which are subject to segmentation and reassembly and are transferred as encapsulated PDU fragments to the MAC Sublayer 31.
Processing within the LAC Sublayer 32 is done sequentially, with processing entities passing the partially formed LAC PDU to each other in a well-established order. SDUs and PDUs are processed and transferred along functional paths, without the need for the upper layers to be aware of the radio characteristics of the physical channels. However, the upper layers could be aware of the characteristics of the physical channels and may direct Layer 2 30 to use certain physical channels for the transmission of certain PDUs.
A 1×EV-DO system is optimized for packet data service and characterized by a single 1.25 MHz carrier (“1×”) for data only or data Optimized (“DO”). Furthermore, there is a peak data rate of 2.4 Mbps or 3.072 Mbps on the forward Link and 153.6 Kbps or 1.8432 Mbps on the reverse Link. Moreover, a 1×EV-DO system provides separated frequency bands and internetworking with a 1× System. FIG. 10 illustrates a comparison of cdma2000 for a 1× system and a 1×EV-DO system.
In CDMA2000, there are concurrent services, whereby voice and data are transmitted together at a maximum data rate of 614.4 kbps and 307.2 kbps in practice. An MS 2 communicates with the MSC 5 for voice calls and with the PDSN 12 for data calls. A cdma2000 system is characterized by a fixed rate with variable power with a Walsh-code separated forward traffic channel.
In a 1×EV-DO system, the maximum data rate is 2.4 Mbps or 3.072 Mbps and there is no communication with the circuit-switched core network 7. A 1×EV-DO system is characterized by fixed power and a variable rate with a single forward channel that is time division multiplexed.
FIG. 11 illustrates a 133 EV-DO system architecture. In a 1×EV-DO system, a frame consists of 16 slots, with 600 slots/sec, and has a duration of 26.67 ms, or 32,768 chips. A single slot is 1.6667 ms long and has 2048 chips. A control/traffic channel has 1600 chips in a slot, a pilot channel has 192 chips in a slot and a MAC channel has 256 chips in a slot. A 1×EV-DO system facilitates simpler and faster channel estimation and time synchronization,
FIG. 12 illustrates a 1×EV-DO default protocol architecture. FIG. 13 illustrates a 1×EV-DO non-default protocol architecture.
Information related to a session in a 1×EV-DO system includes a set of protocols used by an MS 2, or access terminal (AT), and a BS 6, or access network (AN), over an airlink, a Unicast Access Terminal Identifier (UATI), configuration of the protocols used by the AT and AN over the airlink and an estimate of the current AT location.
The Application Layer provides best effort, whereby the message is sent once, and reliable delivery, whereby the message can be retransmitted one or more times. The stream layer provides the ability to multiplex up to 4 (default) or 255 (non-default) application streams for one AT 2.
The Session Layer ensures the session is still valid and manages closing of session, specifies procedures for the initial UATI assignment, maintains AT addresses and negotiates/provisions the protocols used during the session and the configuration parameters for these protocols.
FIG. 14 illustrates the establishment of a 1×EV-DO session. As illustrated in FIG. 14, establishing a session includes address configuration, connection establishment, session configuration and exchange keys.
Address configuration refers to an Address Management protocol assigning a UATI and Subnet mask. Connection establishment refers to Connection Layer Protocols setting up a radio link. Session configuration refers to a Session Configuration Protocol configuring all protocols. Exchange key refers a Key Exchange protocol in the Security Layer setting up keys for authentication.
A “session’ refers to the logical communication link between the AT 2 and the RNC, which remains open for hours, with a default of 54 hours. A session lasts until the PPP session is active as well. Session information is controlled and maintained by the RNC in the AN 6.
When a connection is opened, the AT 2 can be assigned the forward traffic channel and is assigned a reverse traffic channel and reverse power control channel. Multiple connections may occur during single session.
The Connection Layer manages initial acquisition of the network and communications. Furthermore, the Connection Layer maintains an approximate AT 2 location and manages a radio link between the AT 2 and the AN 6. Moreover, the Connection Layer performs supervision, prioritizes and encapsulates transmitted data received from the Session Layer, forwards the prioritized data to the Security Layer and decapsulates data received from the Security Layer and forwards it to the Session Layer.
FIG. 15 illustrates Connection Layer Protocols.
In the Initialization State, the AT 2 acquires the AN 6 and activates the initialization State Protocol. In the Idle State, a closed connection is initiated and the Idle State Protocol is activated. In the Connected State, an open connection is initiated and the Connected State Protocol is activated.
A closed connection refers to a state where the AT 2 is not assigned any dedicated air-link resources and communications between the AT and AN 6 are conducted over the access channel and the control channel. An open connection refers to a state where the AT 2 can be assigned the forward traffic channel, is assigned a reverse power control channel and a reverse traffic channel and communication between the AT 2 and AN 6 is conducted over these assigned channels as well as over the control channel.
The Initialization State Protocol performs actions associated with acquiring an AN 6. The Idle State Protocol performs actions associated with an AT 2 that has acquired an AN 6, but does not have an open connection, such as keeping track of the AT location using a Route Update Protocol. The Connected State Protocol performs actions associated with an AT 2 that has an open connection, such as managing the radio link between the AT and AN 6 and managing the procedures leading to a closed connection. The Route Update Protocol performs actions associated with keeping track of the AT 2 location and maintaining the radio link between the AT and AN 6. The Overhead Message Protocol broadcasts essential parameters, such as QuickConfig, SectorParameters and AccessParameters message, over the control channel. The Packet Consolidation Protocol consolidates and prioritizes packets for transmission as a function of their assigned priority and the target channel as well as providing packet de-multiplexing on the receiver.
The Security Layer includes a key exchange function, authentication function and encryption function. The key exchange function provides the procedures followed by the AN 2 and AT 6 for authenticating traffic. The authentication function provides the procedures followed by the AN 2 and AT 6 to exchange security keys for authentication and encryption. The encryption function provides the procedures followed by the AN 2 and AT 6 for encrypting traffic.
The 1×EV-DO forward Link is characterized in that no power control and no soft handoff is supported. The AN 6 transmits at constant power and the AT 2 requests variable rates on the forward Link. Because different users may transmit at different times in TDM, it is difficult to implement diversity transmission from different BS's 6 that are intended for a single user.
In the MAC Layer, two types of messages originated from higher layers are transported across the physical layer, specifically a User data message and a signaling message. Two protocols are used to process the two types of messages, specifically a forward traffic channel MAC Protocol for the User data message and a control channel MAC Protocol, for the signaling message.
The Physical Layer is characterized by a spreading rate of 1.2288 Mcps, a frame consisting of 16 slots and 26.67 ms, with a slot of 1.67 ms and 2048 chips. The forward Link channel includes a pilot channel, a forward traffic channel or control channel and a MAC channel.
The pilot channel is similar to the to the cdma2000 pilot channel in that it comprises all “0” information bits and Walsh-spreading with W0 with 192 chips for a slot.
The forward traffic channel is characterized by a data rate that varies from 38.4 kbps to 2.4576 Mbps or from 4.8 kbps to 3.072 Mbps. Physical Layer packets can be transmitted in 1 to 16 slots and the transmit slots use 4-slot interlacing when more than one slot is allocated. If ACK is received on the reverse Link ACK channel before all of the allocated slots have been transmitted, the remaining slots shall not be transmitted.
The control channel is similar to the sync channel and paging channel in cdma2000. The control channel is characterized by a period of 256 slots or 427.52 ms, a Physical Layer packet length of 1024 bits or 128, 256, 512 and 1024 bits and a data rate of 38.4 kbps or 76.8 kbps or 19.2 kbps, 38.4 kbps or 76.8 kbps.
The 1×EV-DO reverse link is characterized in that the AN 6 can power control the reverse Link by using reverse power control and more than one AN can receive the AT's 2 transmission via soft handoff. Furthermore, there is no TDM on the reverse Link, which is channelized by Walsh code using a long PN code.
An access channel is used by the AT 2 to initiate communication with the AN 6 or to respond to an AT directed message. Access channels include a pilot channel and a data channel.
An AT 2 sends a series of access probes on the access channel until a response is received from the AN 6 or a timer expires. An access probe includes a preamble and one or more access channel Physical Layer packets. The basic data rate of the access channel is 9.6 kbps, with higher data rates of 19.2 kbps and 38.4 kbps available.
When more that one AT 2 is paged using the same Control channel packet, Access Probes may be transmitted at the same time and packet collisions are possible. The problem can be more serious when the ATs 2 are co-located, are in a group call or have similar propagation delays.
One reason for the potential of collision is the inefficiency of the current persistence test in conventional methods. Because an AT 2 may require a short connection setup time, a paged AT may transmit access probes at the same time as another paged AT when a persistence test is utilized.
Conventional methods that use a persistence test are not sufficient since each AT 2 that requires a short connection setup times and/or is part of a group call may have the same persistence value, typically set to 0. If AT's 2 are co-located, such as In a group call, the Access Probes arrive at the An 6 at the same time, thereby resulting in access collisions and increased connection setup time.
Therefore, there is a need for a more efficient approach for access probe transmission from co-located mobile terminals requiring short connection times. The present invention addresses this and other needs such as interference cancellation.
In a wireless communication system, signals often distorted through fading channels before the signals reach the receiving end. To address this problem, as discussed above, various signal processing schemes for restoring desired signals caused by distortions are employed at the receiving end as wells as at the transmitting end.
Many frequency domain signal processing techniques are available for processing the received time domain signals such as frequency domain channel equalization of received block time domain signals. However, when fast Fourier transform (FFT) and/or discrete Fourier transform (DFT) are applied to received signals, time aliasing problem can occur.
To aid the receiving end estimate channel response, the transmitting side can perform a preprocessing operation. That is, the transmitting side can perform special placement of the pilot symbols and the data symbols by placing a silent period before transmitting each pilot sub-block. To put differently, the pilot symbols and the data symbols are separated.
In transmitting data, it is undesirable to have the data portion interference with the pilot portion. As such, as mentioned above, a silent period or a silent block can be used. The silent period or the silent block can be a null symbol. More specifically, the silent block/period can be placed after the data symbol and before the pilot symbol. Alternatively, the silent block (e.g., null symbol) can be placed between a pilot symbol and a data symbol at the transmitting end. The silent period can be used to separate the data with the pilot.
FIG, 16 illustrates a placement of a silent block/period relative to a pilot block and a data block at the transmitting end. As illustrated in FIG. 16, there is a silent period before transmitting the pilot block by the transmitting end. To put differently, the data block and the pilot block are separated by a silent block.
FIG. 16 may serve various purposes including mitigating interference effects on pilot blocks so that channel estimation and equalization can be more accurately performed, diagonalizing channel response matrix, and saving transmitter power and mitigating possible interferences especially in cellular systems.
By this arrangement at the transmitting end, possible interference can be eliminated or minimized when transmitting the data symbols and the pilot symbols. Further, with this arrangement, timing offset can be addressed. More specifically, assume a transmitting end transmitting using more than two antennas (e.g., Multi-Input, Multi-Output system). Even if the data symbols and the pilot symbols are transmitted at the same time, as a result of possible delay during transmission, the receiving end may not receive the transmitted symbols at the same time. In other words, the receiving end may experience timing offset in reception. By placing the silent block placed between the data symbol and the pilot symbol, the timing offset can be compensated. That is, the silent block can be used to cover or compensate for the received time difference.
At the receiving end, the receiver signal processing can be simplified for to better estimate channel response. FIG. 17 illustrates a placement of a silent block relative to a pilot block and a data block at the receiving end. With this preprocessing approach, diagonalization of channel response matrix for the next one-tap channel equalization in frequency domain is made simpler. In this embodiment, as illustrated in FIG. 18, the silent block or silent period is added or placed in front of the data block as well as between the data block and the pilot block. With this arrangement for example, the receiving end does not need to take any action since the silent block or null symbol is represented with zeroes whereas in conventional cases, a cyclic prefix is removed at the receiving end.
It is possible to adjust the size or length of the silent block according to the channel condition. For example, if the channel condition is poor, the silent block or the silent period can be made longer so as to compensate for possible delay and/or interferences in transmission. Alternatively, if the channel condition is excellent, the length of the silent period/block can be shortened or even removed.
In the next FFT/DFT procedure, which is used to transform time domain signals to the corresponding frequency domain signals, the FFT/DFT length can be equal to the length of available signals instead of using a doubled or longer length for avoiding time-aliasing problem. For example, if a frequency domain channel estimation on a block of received signals r=[r₁r₂. . . r_N]^Tof N samples is to be performed, a typical way is to use M-point DFT/FFT to avoid time-aliasing problem with M≧2N. By applying the aforementioned processing technique, in which the FFT/DFT length is equal to the length of the available signals, a smaller N-point FFT/DFT rather than a larger M-point DFT/FFT is necessary. Consequently, computation complexity associated with FFT/DFT processing can be simplified and reduced in the subsequent frequency domain channel equalization.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

1. A method of transmitting at least one packet in a wireless mobile communication system, the method comprising transmitting at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol.

2. The method of claim 1, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each packet.

3. The method of claim 1, wherein each packet comprises at least one subpacket.

4. The method of claim 3, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each subpacket.

5. The method of claim 1, wherein the null symbol is zero-padded.

6. The method of claim 1, wherein the null symbol has a variable duration.

7. The method of claim 6, wherein the variable duration is set between 0 and a predetermined maximum value.

8. The method of claim 1, wherein the wireless mobile communication system implements any one of Orthogonal Frequency Division Multiplexing (OFDM), Code Division Multiplexing (CDM), Code Division Multiple Access (CDMA), Multi-Carrier Code Division Multiplexing (MC-CDM), or Multi-Carrier Code Division Multiple Access (MC-CDMA).

9. The method of claim 1, wherein the at least one packet is transmitted in a time-domain.

10. A method of transmitting at least one packet in a wireless mobile communication system, the method comprising transmitting at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each packet.

11. A method of receiving at least one packet in a wireless mobile communication system, the method comprising:

receiving at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is transmitted between transmission of the pilot symbol and the data symbol.

12. The method of claim 11, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each packet.

13. The method of claim 11, wherein each packet comprises at least one subpacket.

14. The method of claim 13, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each subpacket.

15. The method of claim 11, wherein the null symbol is zero-padded.

16. The method of claim 1 1, wherein the null symbol has a variable duration.

17. A packet configured to transmit data from a transmitting end to a receiving end in a wireless communication system, the packet comprising:

at least one pilot symbol, at least one data symbol, and at least one null symbol, wherein the at least one null symbol is placed between at least one pilot symbol and the at least one data symbol.

18. The method of claim 17, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each packet.

19. The method of claim 17, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each packet.

20. The method of claim 19, wherein the at least one pilot symbol, the at least one data symbol, and the at least one null symbol are provided in each subpacket.