3GPP aims to develop 5G specifications that enable use cases for several vertical domains such as Industrial, Power, Automotive, home automation, military, agriculture, to name a few, besides providing significant improvements for the legacy domain use cases. One such additional vertical for which 3GPP standardization is on-going is the Maritime Communications

It is foreseen that the legacy radio technologies used in the maritime communication would suffer capacity and data rate issues when new use cases like e-Navigation and Maritime Autonomous Surface Ships (MASS) are implemented as planned by International Maritime Organization (IMO). 3GPP is coordinating with various maritime industries and government bodies in order to collect/identify the stage 1 requirements which then form the basis for stage 2 and stage 3 specifications in order to enhance 5G REL 15 specifications to support maritime scenarios.

The high level objectives of FS_MARCOM, a 5G SID [2], in 3GPP are:

COMMERCIAL OBJECTIVES:

• Provide communication services between users at sea and users at land (example maritime authorities) or communication services among users at sea
• Enable enhanced Machine Type Communications (eMTC) among UEs at sea, between UEs at sea and UEs at land, vessel to vessel communications.
• Provide enhanced mobile broadband (eMBB) services there by increasing the information availability at sea
• Improve radio coverage and provide higher data rates at sea
• Interworking between the existing/future maritime radio communication systems (such as VDES) and 3GPP 5G systems

OPERATIONAL/SHIPPING EFFICIENCY OBJECTIVES:

• Some of the vessel to vessel communications scenarios could include, goods management (tracking, status), journey management (real time tracking, planning, optimization and navigation safety), machinery management (failures, predictive maintenance), personnel services (voice, video and data)

PUBLIC SAFETY OBJECTIVES:

• Provide mission critical communications between authorities at land and authorities at sea (maritime police) to improve maritime safety and maritime environment

The above objectives inherently also means to extend/enable the following existing 3GPP 5G use cases and services to the maritime scenario:

• Mobile services such as voice and data calls, real time audio/video streaming, mobile TV etc
• Machine Type Communications such as eMTC and NBIoT
• Public Warning Services PWS and ePWS
• Machine critical services on and off network
• Enabling technologies developed by 5GSAT (study item to enable 5G access over satellite) and 5GLAN (study item to enable LAN type services using 5G technologies) 
• Indoor positioning services developed by 5G_HYPOS (study item for positioning)

The following use cases/services are planned for the maritime scenario in 5G:

USE CASES ON MOBILE BROADBAND SERVICES FOR USERS ON SEA:

• Video streaming service in the cabin or the deck of the vessel
• Transitions between IOPS mode and on-network mode
• Support of Positioning Technologies
• Support of LAN type services on 5G

USE CASES ON MACHINE TYPE COMMUNICATIONS:

• Communication between wearable IoT devices and Maritime Rescue Coordination Centre (MRCC)
• Mobility management for group of UEs on a vessel
• Push to location service among vessels
• Small cell deployment in each cabin of the vessel

USE CASES ON MARITIME COMMUNICATIONS BETWEEN AUTHORITIES AND USERS AT SEA:

• Communications for search and rescue
• Coastal and local warning service
• Pilotage Service
• Tugs Service
• Notification of PWS messages to shipboard users
• Urgent Alarm Service

Note that all of the below use cases are not included in the stage 1 TR as of December 2018 owing to the misalignment of the possible IMO decision dates and the 3GPP stage1 requirement standardization dates.

• Vessel Shore Reporting
• VTS Information Service
• Navigational Assistance Service
• Traffic Organization Service
• Local Port Service
• Telemedical Assistance Service
• Maritime Assistance Service
• Nautical Chart Service
• Nautical Publications Service
• Ice Navigation Service
• Meteorological Information Service
• Real Time Hydrographic and Environmental Information Service

USE CASES FOR INTERWORKING AND HARMONIZATION

• Satellite access for maritime communications over 5G System
• Interworking between 5G System and VDES (VHF Data Exchange System)

There are several other study items from 3GPP that would prove useful for the maritime communications standardization:

• Study on NR to support non-terrestrial network – FS_NR_nonterr_nw, 3GPP RAN WG1
• Study on using satellite access in 5G – FS_5GSAT, 3GPP SA WG1
• Study on positioning use cases – FS_5GHYPOS, 3GPP SA WG1
• Study on LAN support in 5G – FS_5GLAN, 3GPP SA WG1

REFERENCES

1. Maritime Communication Services over 3GPP Systems, ETSI workshop
2. Study on Maritime Communication Services over 3GPP System, SP-170453
3. Feasibility Study on Maritime Communication Services over 3GPP System, TR 22.819
4. New WID on Maritime Communication Services over 3GPP System, SP-180594
5. Maritime Communication Services over 3GPP System, TS 22.119 

Compressed mode in UMTS is an important concept that enables functionality such as inter-frequency and inter-system/inter-RAT (Radio Access Technology) handovers. Compressed mode is the mode in which the transmitter (base band) on Node B and/or User Equipment (UE) creates gaps in its transmission in Downlink and/or Uplink in order for the UE receiver to tune its receive frequency to the non-used desired frequency and perform measurements.

Not all UEs require the compressed mode to perform measurements. Some advanced terminals come with dual RF receiver capability in which they will be able to receive simultaneously on two carriers. Such mobiles would be able to make inter frequency measurements even without compressed mode configurations. However, when the UE capability does not allow it to make measurements on the non-used frequency (ie, other than the currently used frequency on which the UE has camped on), it can utilize the transmission gaps in the compressed frames to make measurements on the desired frequency.

UEs that require compressed mode for inter frequency measurements shall support one transmission gap sequence for each measurement purpose in FDD. More than one transmission gap pattern can be active at a time if the UE supports several measurement purposes. However, higher layers ensure that gaps from different transmission gap patterns do not overlap. The following measurement purposes are applicable:

• FDD
• TDD
• GSM Carrier RSSI Measurement
• Initial BSIC Identification
• BSIC re-confirmation
• E-UTRA

There are two ways by which a transmission gap can be achieved at the transmitter:

• Compressed Mode by Higher Layer Scheduling (HLS)
• Compressed Mode by Spreading Factor (SF) Reduction

Before we delve deeper, in subsequent posts, on to how a transmission gap is created in the SF reduction method, it is useful to understand various compressed mode related parameters and how they are related to the physical layer transmission timings. This is the objective of the current post.

The following diagram depicts the relation of Transmission Gap Patterns with respect to Connection Frame Numbers (CFN)

The Transmission Gap Pattern is the pattern consisting of one or two transmission gaps. This pattern is repeated ‘TGPRC’ (Transmission Gap Pattern Repetition Count) number of times. The transmission gap pattern is of length TGPL1. In the above picture the TGPL1 is equal to two frames.

Below figure depicts the details of the Transmission Gap Pattern which is mentioned above.

TGSN (Transmission Gap Starting Slot Number) signify the slot number in which the first gap (TGAP1) of the transmission gap pattern starts. The first transmission gap is of length TGL1 (Transmission Gap Length1). TGD (Transmission Gap start Distance) signify the number of slots from the beginning of the first transmission gap at which second transmission gap (TGAP2) starts. The second transmission gap is of length TGL2 (Transmission Gap Length2). As mentioned earlier, TGPL1 (Transmission Gap Pattern Length) signifies the length in frames of the full transmission gap pattern.

In forth coming posts we would discuss details on how compressed mode affects various procedures, how higher layers configure and control compressed mode, various types of measurements that are carried out in compressed mode.

With the advent of smart phones and innovative applications, recent years have seen a tremendous upsurge of the data demands from users worldwide. Operators around the world, in the current day, are facing multiple challenges in terms of maintaining the profitability, providing superior user satisfaction, deploying innovative services etc. Though data usage trends are on inclining trend, voice revenues still constitute significant portion of mobile operator's revenues, according to a study. Given this scenario, any new technology or feature that differentiates the voice service is certainly a welcome from the operator's point of view and would be a chance to ship more devices from the device vendor's perspective.

High Definition Voice (HD Voice) is one such technology which provides superior voice quality to end users and would certainly be a differentiating service for a mobile operator. First commercial deployment of HD Voice service is carried out by Orange in its network in Moldova in September 2009. Since then the deployments of HD Voice service has seen a steady growth and, today, there exist as many as 36 mobile networks with HD Voice capability.

When initial HD Voice capable networks and devices started to appear, different operators and vendors used different logos to market the HD capability. Operator community joined together to solve this problem and a common logo was proposed as shown in the picture. From the end users perspective, HD Voice provides superior voice quality which means the voice sounds more natural and it would be easy to recognize the caller. The speech would be easier to comprehend even in noisy surroundings.

The technology behind the HD Voice in mobile networks is called Adaptive Multi Rate – Wide Band (AMR – WB). AMR WB is not new and has been in 3GPP standards for a while. AMR WB is a speech coding technology that preserves more frequency components of the original speech in the encoded speech signal. Original AMR has a maximum encoded bit rate of 12.2kbps and it is possible to run the encoder in different other speech coding output rates depending on the quality of the air interface (for example the speech coder can be configured to output a bit rate of 12.2kbps under best radio conditions and when the radio conditions deteriorate it is possible to turn to lower speech coding bit rates). The original analog speech signal picked up by the microphone is sampled at 8 KHz (according to Nyquist criteria, the sampling frequency needs to be at least twice the highest frequency of the signal undergoing sampling. In the original AMR technology the frequency range of the input signal component is 300 Hz – 3400 Hz). In the WB-AMR technology, the frequency component (range) that is transmitted is increased from (300 Hz-3000 Hz) to (100 Hz-7000 Hz) and hence the sampling frequency increases to 16 KHz from 8 KHz. Apart from this, the speech coder is modified accordingly and outputs a maximum data rate of 12.65 kbps. The advantages are: increased voice quality while preserving the voice capacity (ie, no additional air interface capacity is needed to Support AMR-WB). The following picture depicts, as an example, changes needed in the UMTS mobile network in order to support HD Voice (AMR-WB). Note that even though the picture depicts UMTS example, AMR-WB can also be supported in the GSM network.

Handset Support for HD Voice

As indicated, handsets should support AMR-WB speech CoDeC, AMR-WB bearer establishment, must manage transitions between different AMR-WB rates and between AMR-WB and AMR-NB rates (would be useful when the destination network is not supporting the AMR-WB data delivery).

Access Network Support for HD Voice

On the access network side, in the UMTS case, the node B will usually be transparent to the AMR-WB changes; however there will be some revalidation of the Node B software needed in order to verify the support of AMR-WB data rates. RNC shall be capable to admit the AMR-WB Radio Access Bearer (RAB) and its combinations with PS bearers (in case a Packet Switch call is initiated in parallel or during the ongoing AMR-WB speech call) and shall be able to manage transitions among AMR-WB (radio quality adaptation)

Core Network (CN) Support for HD Voice

In the Core Network which is based on the 64 kbps circuit switch links, the speech data (AMR or any other speech encoded data) is trans-coded in to 64 kbps PCM data. The 64 kbps PCM data is again converted back to original speech encoded data rate in the destination network before the data is finally decoded in the mobile phone using appropriate speech decoder. This kind of trans-coding on to 64 kbps introduces additional complexity to network nodes and also contributes to additional end to end speech delay. With the introduction of Bearer Independent Core Network (BCIN), links between RNC and CN and also the CN back bone are based on the ATM or IP links. This makes it possible to transport the speech data without additional trans-coding performed at CN. This further leads to the possibility to deactivate the transcoders when BCIN functionality is available. However, it is important to note that this is applicable to the case in which the entire call travels only through UMTS network. This is called Transcoding Free Operation (TrFO). In case when either of the users is in GSM network, transcoding is mandatory since the interface between BSC and the CN (A interface) is always PCM based. So, in case of a GSM network, transcoders automatically come in to picture due to the inherent PCM link presence. However, these transcoders exchange in-band signalling, once call is established, and can eliminate the tandom operation by tunnelling the AMR-WB data in the PCM links (this wastes some BW but the speech quality is preserved). This sort of operation is called Tandom Free Operation (TFO). If the call is landing on a PSTN network then one transcoding in to 64 kbps is needed at the media gateway which connects the core network to PSTN network.