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Channel Coding NR

25 Aug

In 5G NR two type of coding chosen by 3GPP.

  • LDPC : Low density parity check
  • Polar code 

Why LDPC and Polar code chosen for 5G Network

Although many coding schemes with capacity achieving performance at large block lengths are available, many of those do not show consistent good performance in a wide range of block lengths and code rates as the eMBB scenario demands. But turbo, LDPC and polar codes show promising BLER performance in a wide range of coding rates and code lengths; hence, are being considered for 5G physical layer. Due to the low error probability performance within a 1dB fraction from the the Shannon limit, turbo codes are being used in a variety of applications, such as deep space communications, 3G/4G mobile communication in Universal Mobile  Telecommunications System (UMTS) and LTE standards and Digital Video Broadcasting (DVB). Although it is being used in 3G and 4G, it may not satisfy the performance requirements of eMBB for all the code rates and block lengths as the implementation complexity is too high for higher data rates.

Invention of LDPC

LDPC codes were originally invented and published in 1962.

(5G) new radio (NR) holds promise in fulfilling new communication requirements that enable ubiquitous, low-latency, high-speed, and high-reliability connections among mobile devices. Compared to fourth-generation (4G) long-term evolution (LTE), new error-correcting codes have been introduced in 5G NR for both data and control channels. In this article, the specific low-density parity-check (LDPC) codes and polar codes adopted by the 5G NR standard are described.

Turbo codes, prevalent in most modern cellular devices, are set to be replaced by LDPC codes as the code for forward error correction, NR is a pair of new error-correcting channel codes adopted, respectively, for data channels and control channels. Specifically, LDPC codes replaced turbo codes for data channels, and polar codes replaced tail-biting convolution codes (TBCCs) for control channels.This transition was ushered in mainly because of the high throughput demands for 5G New Radio (NR). The new channel coding solution also needs to support incremental-redundancy hybrid ARQ, and a wide range of block lengths and coding rates, with stringent performance guarantees and minimal description complexity. The purpose of each key component in these codes and the associated operations are explained. The performance and implementation advantages of these new codes are compared with those of 4G LTE.

Why LDPC ?

  • Compared to turbo code decoders, the computations for LDPC codes decompose into a larger number of smaller independent atomic units; hence, greater parallelism can be more effectively achieved in hardware.
  • LDPC codes have already been adopted into other wireless standards including IEEE 802.11, digital video broadcast (DVB), and Advanced Television System Committee (ATSC).
  • The broad requirements of 5G NR demand some innovation in the LDPC design. The need to support IR-hybrid automatic repeat request (HARQ) as well as a wide range of block sizes and code rates demands an adjustable design.
  • LDPC codes can offer higher coding gains than turbo codes and have lower error floors.
  • LDPC codes can simultaneously be computationally more efficient than turbo codes, that is, require fewer operations to achieve the same target block error rate (BLER) at a given energy per symbol (signal-to noise ratio, SNR)
  • Consequently, the throughput of the LDPC decoder increases as the code rate increases.
  • LDPC code shows inferior performance for short block lengths (< 400 bits) and at low code rates (< 1/3) [ which is typical scenario for URLLC and mMTC use cases. In case of TBCC codes, no further improvements have been observed towards 5G new use cases.

 

 The main advantages of 5G NR LDPC codes compared  to turbo codes used in 4G LTE 

 

  •         1.Better area throughput efficiency (e.g., measured in Gb/s/mm2) and substantially                 higher achievable peak throughput.
  •         2. reduced decoding complexity and improved decoding latency (especially when                     operating at high code rates) due to higher degree of parallelization.
  •        3. improved performance, with error floors around or below the block error rate                       (BLER) 10¯5 for all code sizes and code rates.

These advantages make NR LDPC codes suitable for the very high throughputs and ultra-reliable low-latencycommunication targeted with 5G, where the targeted peak data rate is 20 Gb/s for downlink and 10 Gb/s for uplink.

 

Structure of LDPC

 

Structure of NR LDPC Codes

 

The NR LDPC coding chain contain

  • code block segmentation,
  • cyclic-redundancy-check (CRC)
  • LDPC encoding
  • Rate matching
  • systematic-bit-priority interleaving

code block segmentation allows very large transport blocks to be split into multiple smaller-sized code blocks that can be efficiently processed by the LDPC encoder/decoder. The CRC bits are then attached for error detection purposes. Combined with the built-in error detection of the LDPC codes through the parity-check (PC) equations, very low probability of undetected errors can be achieved. The rectangular interleaver with number of rows equal to the quadrature amplitude modulation (QAM) order improves performance by making systematic bits more reliable than parity bits for the initial transmission of the code blocks.

NR LDPC codes use a quasi-cyclic structure, where the parity-check matrix (PCM) is defined by a smaller base matrix.Each entry of the base matrix represents either a Z # Z zero matrix or a shifted Z # Z identity matrix, where a cyclic shift (given by a shift coefficient) to the right of each row is applied.

The LDPC codes chosen for the data channel in 5G NR are quasi-cyclic and have a rate-compatible structure that facilitates their use in hybrid automatic-repetition-request (HARQ) protocols

General structure of the base matrix used in the quasi-cyclic LDPC codes selected for the data channel in NR.

To cover the large range of information payloads and rates that need to be supported in 5G NR,
two different base matrices are specified.

Each white square represents a zero in the base matrix and each nonwhite square represents a one.

The first two columns in gray correspond to punctured systematic bits that are actually not transmitted.

The blue (dark gray in print version) part constitutes the kernel of the base matrix, and it defines a high-rate code.

The dual-diagonal structure of the parity subsection of the kernel enables efficient encoding. Transmission at lower code rates is achieved by adding additional parity bits,

The base matrix #1, which is optimized for high rates and long block lengths, supports LDPC codes of a nominal rate between 1/3 and 8/9. This matrix is of dimension 46 × 68 and has 22 systematic columns. Together with a lift factor of 384, this yields a maximum information payload of k = 8448 bits (including CRC).

The base matrix #2 is optimized for shorter block lengths and smaller rates. It enables transmissions at a nominal rate between 1/5 and 2/3, it is of dimension 42 × 52, and it has 10 systematic columns.
This implies that the maximum information payload is k = 3840.

 

Polar Code 

Polar codes, introduced by Erdal Arikan in 2009 , are the first class of linear block codes that provably achieve the capacity of memoryless symmetric  (Shannon) capacity of a binary input discrete memoryless channel using a low-complexity decoder, particularly, a successive cancellation (SC) decoder. The main idea of polar coding  is to transform a pair of identical binary-input channels into two distinct channels of different qualities: one better and one worse than the original binary-input channel.

Polar code is a class of linear block codes based on the concept of Channel polarization. Explicit code construction and simple decoding schemes with modest complexity and memory requirements renders polar code appealing for many 5G NR applications.

Polar codes with effortless methods of puncturing (variable code rate) and code shortening (variable code length) can achieve high throughput and BER performance better.

At first, in October 2016 a Chinese firm Huawei used Polar codes as channel coding method in 5G field trials and achieved downlink speed of 27Gbps.

In November 2016, 3GPP standardized polar code as dominant coding for control channel functions in 5G eMBB scenario in RAN 86 and 87 meetings.

Turbo code is no more in the race due to presence of error floor which make it unsuitable for reliable communication.High complexity iterative decoding algorithms result in low throughput and high latency. Also, the poor performance at low code rates for shorter block lengths make turbo code unfit for 5G NR.

Polar Code is considered as promising contender for the 5G URLLC and mMTC use cases,It offers excellent performance with variety in code rates and code lengths through simple puncturing and code shortening mechanisms respectively

Polar codes can support 99.999% reliability which is mandatory for  the ultra-high reliability requirements of 5G applications.

Use of simple encoding and low complexity SC-based decoding algorithms, lowers terminal power consumption in polar codes (20 times lower than turbo code for same complexity).

Polar code has lower SNR requirements than the other codes for equivalent error rate and hence, provides higher coding gain and increased spectral efficiency.

Framework of Polar Code in 5G Trial System

The following figure is shown for the framework of encoding and decoding using Polar code. At the transmitter, it will use Polar code as channel coding scheme. Same as in Turbo coding module, function blocks such as segmentation of Transmission Block (TB) into multiple Code Blocks (CBs), rate matching (RM) etc. are also introduced when using Polar code at the transmitter. At the receiver side, correspondingly, de-RM is firstly implemented, followed by decoding CB blocks and concatenating CB blocks into one TB block. Different from Turbo decoding, Polar decoding uses a specific decoding scheme, SCL to decode each CB block. For the encoding and decoding framework of Turbo.

  NR polar coding chain

 

Source: https://cafetele.com/channel-coding-in-5g-new-radio/

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In-Car Entertainment in Indonesia

22 Nov

Industry Reports

Through 2011, in-car entertainment remained the smallest category within consumer electronics in Indonesia. The category is niche, gearing towards middle- and upper-income classes. Growth of in-car entertainment is strong even though it is still in small size. Jakarta, the capital city, is particularly known for its bad traffic conditions, and other first-tier cities in the country have shown the same problem. Therefore, there is a rising demand for high-quality in-car entertainment to keep…

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Cloud Telephony Firm Infratel Gets $3 Million Investment from Runa, Prostor

8 Aug

An illustration of Infratel’s Infra Cloud Receptionist technology, which the company will develop further with funds from Runa Capital and Prostor Capital

Cloud telephony provider Infratel announced on Tuesday that it has secured $3 million in Series A funding from investment firms Prostor Capital and Runa Capital, money it intends to use on building out its platform for small businesses.

Runa Capital is an investment firm with close ties to the hosting industry. Started just over a year ago by a group that includes former Parallels CEO (and current chair and chief architect) Serguei Beloussov and 1&1 Internet founders Andreas Gauger and Achim Weiss, as well as several others. Runa has focused on investing in software companies that address some of the needs of the hosting market, or could benefit from using hosting providers as a channel.

That list includes NGINX, Ecwid and Jelastic, and included Infratel prior to today’s announcement, though it may be that Tuesday’s announcement references the original investment in Infratel made previously by Runa.

“The unique technology platform and business model make Infratel a significant acquisition for our portfolio,” says Beloussov, quoted in the press release announcing the investment. “Our long-term relationship, hosting service providers network, and technical expertise can help Infratel in the cloud telephony market to provide unique solutions to millions of small businesses around the world.”

Prostor Capital, says Infratel, is an investment firm with a “deep knowledge of the telephony and service provider industry.”

Infratel’s telephony products, while designed for small businesses, are designed to be distributed through service providers, and through hosting providers in particular. In the press release announcing the investment, Infratel says it has built a “cloud based solution that integrates directly into the provider’s infrastructure,” providing a better ROI for service providers. For Infratel, the advantage of distributing through service providers is a faster, broader market penetration than possible by targeting the fragmented SOHO market directly.

The company’s main offering is a “cloud receptionist” platform that includes a set of telephony tools that enable a small business with limited staff and resources to handle incoming telephone calls in a more “professional” way, and to better manage their responses. In July, the company spun out the “click-to-call” portion of its platform as a separate, entry-level option, based on the popularity of the individual function.

Part of the company’s efforts to approach the hosting market has been the integration of the Infratel tools with the Parallels platform, which Jon McCarrick discussed earlier this year at the Parallels Summit.

“There are more than 11 million small businesses in North America and Europe that have a website but don’t have a basic telephony presence, hindering their ability to interact with customers”, says Bryan Goode, CEO of Infratel, quoted in the press release. “Our goal in closing this investment round with Prostor and Runa is to bring intuitive, easy to use communications solutions to help these small businesses grow and prosper.”

Source: http://www.thewhir.com/web-hosting-news/cloud-telephony-firm-infratel-gets-3-million-investment-from-runa-prostor – Liam Eagle on August 7, 2012

LTE Physical, Logical and Transport Channels

19 Jul

In order that data can be transported across the LTE radio interface, various “channels” are used. These are used to segregate the different types of data and allow them to be transported across the radio access network in an orderly fashion.

Effectively the different channels provide interfaces to the higher layers within the LTE protocol structure and enable an orderly and defined segregation of the data.

3G LTE channel types

There are three categories into which the various data channels may be grouped.

  • Physical channels:   These are transmission channels that carry user data and control messages.
  • Transport channels:   The physical layer transport channels offer information transfer to Medium Access Control (MAC) and higher layers.
  • Logical channels:   Provide services for the Medium Access Control (MAC) layer within the LTE protocol structure.

3G LTE physical channels

The LTE physical channels vary between the uplink and the downlink as each has different requirements and operates in a different manner.

  • Downlink:
    • Physical Broadcast Channel (PBCH):   This physical channel carries system information for UEs requiring to access the network. It only carries what is termed Master Information Block, MIB, messages. The modulation scheme is always QPSK and the information bits are coded and rate matched – the bits are then scrambled using a scrambling sequence specific to the cell to prevent confusion with data from other cells.

      The MIB message on the PBCH is mapped onto the central 72 subcarriers or six central resource blocks regardless of the overall system bandwidth. A PBCH message is repeated every 40 ms, i.e. one TTI of PBCH includes four radio frames.

      The PBCH transmissions has 14 information bits, 10 spare bits, and 16 CRC bits.

    • Physical Control Format Indicator Channel (PCFICH) :   As the name implies the PCFICH informs the UE about the format of the signal being received. It indicates the number of OFDM symbols used for the PDCCHs, whether 1, 2, or 3. The information within the PCFICH is essential because the UE does not have prior information about the size of the control region.

      A PCFICH is transmitted on the first symbol of every sub-frame and carries a Control Format Indicator, CFI, field. The CFI contains a 32 bit code word that represents 1, 2, or 3. CFI 4 is reserved for possible future use.

      The PCFICH uses 32,2 block coding which results in a 1/16 coding rate, and it always uses QPSK modulation to ensure robust reception.

    • Physical Downlink Control Channel (PDCCH) :  The main purpose of this physical channel is to carry mainly scheduling information of different types:
      • Downlink resource scheduling
      • Uplink power control instructions
      • Uplink resource grant
      • Indication for paging or system information

The PDCCH contains a message known as the Downlink Control Information, DCI which carries the control information for a particular UE or group of UEs. The DCI format has several different types which are defined with different sizes. The different format types include: Type 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3, 3A, and 4.

    • Physical Hybrid ARQ Indicator Channel (PHICH) :   As the name implies, this channel is used to report the Hybrid ARQ status. It carries the HARQ ACK/NACK signal indicating whether a transport block has been correctly received. The HARQ indicator is 1 bit long – “0” indicates ACK, and “1” indicates NACK.

      The PHICH is transmitted within the control region of the subframe and is typically only transmitted within the first symbol. If the radio link is poor, then the PHICH is extended to a number symbols for robustness.

  • Uplink:
    • Physical Uplink Control Channel (PUCCH) :   The Physical Uplink Control Channel, PUCCH provides the various control signalling requirements. There are a number of different PUCCH formats defined to enable the channel to carry the required information in the most efficient format for the particular scenario encountered. It includes the ability to carry SRs, Scheduling Requests.

      The basic formats are summarised below:

PUCCH Format

Uplink Control Information

Modulation Scheme

Bits per Sub-frame

Notes

Format 1 SR

N/A

N/A

 
Format 1a 1 bit HARQ ACK/NACK with or without SR

BPSK

1

 
Format 1b 2 bit HARQ ACK/NACK with or without SR

QPSK

2

 
Format 2 CQI/PMI or RI

QPSK

20

 
Format 2a CQI/PMI or RI and 1 bit HARQ ACK/NACK

QPSK + BPSK

21

 
Format 2b CQI/PMI or RI and 2 bit HARQ ACK/NACK

QPSK + BPSK

22

 
Format 3       Provides support for carrier aggregation.
    • Physical Uplink Shared Channel (PUSCH) :   This physical channel found on the LTE uplink is the Uplink counterpart of PDSCH
    • Physical Random Access Channel (PRACH) :   This uplink physical channel is used for random access functions. This is the only non-synchronised transmission that the UE can make within LTE. The downlink and uplink propagation delays are unknown when PRACH is used and therefore it cannot be synchronised.

      The PRACH instance is made up from two sequences: a cyclic prefix and a guard period. The preamble sequence may be repeated to enable the eNodeB to decode the preamble when link conditions are poor.

LTE transport channels

The LTE transport channels vary between the uplink and the downlink as each has different requirements and operates in a different manner. Physical layer transport channels offer information transfer to medium access control (MAC) and higher layers.

  • Downlink:
    • Broadcast Channel (BCH) :   The LTE transport channel maps to Broadcast Control Channel (BCCH)
    • Downlink Shared Channel (DL-SCH) :   This transport channel is the main channel for downlink data transfer. It is used by many logical channels.
    • Paging Channel (PCH) :   To convey the PCCH
    • Multicast Channel (MCH) :   This transport channel is used to transmit MCCH information to set up multicast transmissions.
  • Uplink:
    • Uplink Shared Channel (UL-SCH) :   This transport channel is the main channel for uplink data transfer. It is used by many logical channels.
    • Random Access Channel (RACH) :   This is used for random access requirements.

 

LTE logical channels

The logical channels cover the data carried over the radio interface. The Service Access Point, SAP between MAC sublayer and the RLC sublayer provides the logical channel.

  • Control channels:these LTE control channels carry the control plane information:
    • Broadcast Control Channel (BCCH) :   This control channel provides system information to all mobile terminals connected to the eNodeB.
    • Paging Control Channel (PCCH) :   This control channel is used for paging information when searching a unit on a network.
    • Common Control Channel (CCCH) :   This channel is used for random access information, e.g. for actions including setting up a connection.
    • Multicast Control Channel (MCCH) :   This control channel is used for Information needed for multicast reception.
    • Dedicated Control Channel (DCCH) :   This control channel is used for carrying user-specific control information, e.g. for controlling actions including power control, handover, etc..

 

  • Traffic channels:These LTE traffic channels carry the user-plane data:
    • Dedicated Traffic Channel (DTCH) :   This traffic channel is used for the transmission of user data.
    • Multicast Traffic Channel (MTCH) :   This channel is used for the transmission of multicast data.

It will be seen that many of the LTE channels bear similarities to those sued in previous generations of mobile telecommunications.

Source: http://www.radio-electronics.com/info/cellulartelecomms/lte-long-term-evolution/physical-logical-transport-channels.php

Improving Public Safety via LTE

16 Jul

Imagine what it might be like if emergency workers who respond to horrific catastrophes like hurricanes, tornadoes and earthquakes all were carrying small video cameras. Further image that they could share in real-time the video and other critical information they capture on the scene with colleagues at the site and with the entire emergency response ecosystem. 
The vision of video and rich data being efficiently and effectively share between all critical aspects of public safety emergency response ecosystems — from those onsite to all of their support capabilities and the command and control centers of all agencies for whom the speed of responsivenss is essential is being relized. The advent of 4G LTE mobile broadband is at the core of Alcatel-Lucent’s push to make the vision of public safety communication reality.

As noted by Alcatel-Lucent, most public safety agencies today use digital Professional or Land Mobile Radio (PMR/LMR) networks that are based on the TETRA standard in Europe and most other parts of the world which typically use the 400 MHz band. Project25 is used in the U.S. for essential communication with dedicated radio spectrum in the 700 MHz frequency band. 

The challenge for traditional systems is that while they provide emergency teams the ability to talk securely in a one-to-one or group situations with ‘push-to-talk’ to prioritize speakers, they  cannot accommodate the video and rich data services that now are available to any consumer on a 4G LTE mobile broadband network. This is the situation that Alcatel-Lucent (NewsAlert) is looking to rectify by enabling public safety agencies to have their own dedicated spectrum to avail themselves not just of connectivity and interoperability for basic voice interactions during times of crises, but also to the full panoply of capabilities broadband provides.   

In May, Alcatel-Lucent and Cassidian, an EADS (NewsAlert) company, unveiled the Evercor solution, which brings 4G LTE (NewsAlert) mobile broadband to professional mobile radio users in the 400 MHz frequency band.

“It integrates LTE mobile data with mission critical voice capabilities enabling real-time video, collaboration and data services,” said Philippe Keryer, Executive Vice President of Alcatel-Lucent Networks Group and Jean-Marc Nasr, Senior Vice President of Head of Cassidian Secure Communications Solutions, in an announcement about the solution.

Delivering backhaul networking capabilities that can support the power, bandwidth and speeds needed for effective emergency video and data services has also been at the core of Alcatel-Lucent’s public safety work. The company leverages its Wireless Packet Core portfolio, including its all-Internet Protocol/Multiprotocol Label Switching (IP/MPLS) communications protocol and its family of IP/MPLS Service Routers such as its  7705 Service Aggregation Router.

Last August, the company demonstrated its ‘Striker 1’ mobile command vehicle, which the company said, “provides LTE mobile broadband support in the public safety band 14 spectrum for mobile devices such as tablets, radios and video cameras.”

Alcatel-Lucent’s work with public safety agencies around the world on incorporating 4G LTE mobile broadband into their response effort is reflected in two recent projects. It assisted the City of Charlotte on giving fingerprint and face recognition to first responders over the 700 MHz frequency. And, it is working with the São Paolo, Brazil military police to leverage high-speed video and data at two of its police operational centers.

We hear a lot about the revolution 4G LTE is bringing to personal and commercial markets. In various major catastrophes around the world in the past few years, significant gaps in connectivity and capabilities have exposed the critical need for dedicated wireless broadband to enable first responders and aid providers to be able to act quickly and coordinate activities decisively in times where every second matters. It is encouraging how LTE is being used in dedicated frequencies and not just traditional but innovative ways to greatly improve public safety ecosystem response capabilities.    
July 15, 2012 By Mae Kowalke, TMCnet Contributor

Edited by Peter Bernstein

Source: http://next-generation-communications.tmcnet.com/topics/dynamic-enterprise/articles/298869-improving-public-safety-via-lte.htm

Basic Function of Uplink & Downlink Transport Channel in LTE

12 Jul

Basic Function of Uplink & Downlink Transport Channel in LTE

Downlink Transport Channel

Broadcast Channel (BCH)

  • A fixed TF
  • Used for transmission of parts of BCCH, so called MIB

Paging Channel (PCH)

  • Used for transmission of paging information from PCCH
  • Supports discontinuous reception (DRX)

Downlink Shared Channel (DL-SCH)

  • Main transport channel used for transmission of downlink data in LTE
  • Used also for transmission of parts of BCCH, so called SIB
  • Supports discontinuous reception (DRX)

Multicast Channel (MCH)

  • Used to support MBMS

 

Uplink Transport Channel

Uplink Shared Channel (UL-SCH)

  • Uplink counterpart to the DL-SCH

Random Access Channel(s) (RACH)

  • Transport channel which doesn’t carry transport blocks
  • Collision risk

 

Mr.Teletopix / July 4, 2012

Source: http://www.teletopix.org

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