1. What kinds of certification shall a router device get before it is put into market in your country?

In our country,  Nepal Telecommunications Authority (NTA) approves equipment based on a test reports and certificate of conformity issued by the manufacturers by NTA-approved international standardization bodies or regulatory inspection or certifying bodies. A router device needs to get type approved from  NTA, the authority will further verify the Suppliers’ Declaration of Conformity (SDoC) and related standards test reports. Local representative in Nepal will apply on behalf of the manufacturer to NTA requesting Type Approval on its products. If manufacturer is in Nepal then it does not have to have local representative to carry out type approval process. Only Type Approved equipment are allowed to be imported for those, which are specified. NTA or Authorized organization/lab can verify certifications anytime it wishes. NTA has provisions to get type approval of following devises: Low Power Devices (LPDs) or Short Range Devices (SRDs) WLAN - WiFi, Bluetooth, and other 802.11x standard devices having 4W (max. EIRP) & 1 Wi-Max. transmitter output power, Freq: 2.4 GHz and 5 GHz Bands.

2. Please introduce one certification system you familiar with. Also, introduce its advantages, operation mechanism and its effect.

In Nepal all the handset needs to get type approved before it gets to the market as per the provision of Clause (f) of Section 13 and Section 14 of the Telecommunications Act 2016 the Nepal telecommunications Authority determines and/or approves the standard and quality standard of the plant and equipment relating to the telecommunications and the telecommunications service. prior to import and/or sale of any types of radio telecommunication CPEs in Nepal., the concerned manufacturers/authorized agents/representatives have to get type approval certificate under the provision of type approval procedure defined by the Authority  Local representative in Nepal shall apply on behalf of the manufacturer requesting Type Approval on its. A manufacturer can directly apply to the Authority for Type Approval if it is a Nepali Company .Only Type Approved equipment are allowed to be imported for those, which are specified, mentioned  in section 7 under Equipment Identified for Type Approval. It is also noted that the Type Approval Certificate is not an import license and the separate Import/Usage license may be required to import/use the product as per rules of Government of Nepal, wherever applicable. The Authority or a person/s designated by the Authority shall have the right to verify certifications anytime.

To ensure that a mobile phone meets its required standards it has to undergo a variety of types of test. These are often categorized into different areas. In order to undertake these tests different test house may be required, the Type approval of Handsets consists of :.

§  Basic safety testing     This is a form of test that every piece of equipment, whether mobile phone or otherwise has to undergo to ensure that it is intrinsically safe to use and no injury will be inflicted for example from sharp edges, etc.

§  AR, Specific Absorption Rate     This test involves measuring the amount of radio frequency power that a human head will absorb when the cell phone is transmitting. The test uses an anatomically correct model of the human head. Inside the model temperature sensors are set up to measure the temperature rises to ensure that the heating effects caused by the cell phone fall below acceptable limits.

• Protocol testing     One of the major areas of cellular conformance testing is the protocol testing of the cell phone. With the complicated protocols used in mobile phones this is a critical area. If the phone protocol software operates incorrectly then it could result not only in problems experienced by the phone, but also on the network. In view of the complexity of the protocols that are used this testing can be very involved. Specialised network simulators are used. These testers emulate a variety of network entities, i.e. base stations or Node B's (in the case of UMTS), RNCs (Radio Network Controller and the like. In this way a host of scenarios from registration to handover, and in fact any situation that can be encountered can be simulated.

• RF testing     Conformance testing also includes testing of the RF signal. Many measurements of the transmitter and receiver performance are undertaken in a variety of areas such as the out of band emissions. Measurements of the Radio Resource Management (RRM) are undertaken to ensure that the control capability of the phone is operating correctly. There are for instance very tight limits on the control of the transmitter output power to ensure that the cell phone radiates only as much as is needed under any given conditions and noise in the phone bands is reduced to the minimum level. To achieve this testing a protocol tester is often used to control the phone and set up the relevant scenarios. In addition to this an RF measurement and generation equipment is required. This is often in the form of additional signal generators, power meters, analysers, noise generators, etc. To check operation of the phone with multi-path and fading, special fading simulators are required.
• SIM card testing     Another very important area of cellular conformance or interoperability testing is the operation of the SIM card, or in the case of UMTS the USIM. As SIMs are interchangeable between phones it is necessary to rigorously check the interface. It is also vital to check the security aspects of the operation of the SIM, as lapses in security could compromise elements of the network security. To undertake this testing a SIM simulator (or USIM simulator) is required. This simulator emulates the operation of the SIM, and tests on the phone can then be run using a protocol tester to set up the variety of scenarios that are needed.
• Audio tests     Finally audio checks of the cell phone are undertaken. These check the correct operation of the audio aspects of the cellular phone, both in terms of the microphone and the earphone. Checks of audio levels, quality and much more are measured using a variety of audio equipment to ensure they conform to the requirements laid down.

3. Please summarize the major key technologies developed by LTE and LTE-Advanced.

Long Term Evolution (LTE) will ensure the competitiveness of UMTS for the next ten years and beyond by providing a high-data rate, low-latency and packet-optimized system. Also known as E-UTRA (Evolved Universal Terrestrial Radio Access), LTE is part of 3GPP Release 8 specifications. LTE can be operated in either frequency division duplex (FDD) or time division duplex (TDD) mode, also referred to as LTE FDD and TD-LTE. The main key technology aspects of LTE are:

• New, Orthogonal Frequency Division Multiple Access (OFDMA) based multiple access schemes for both LTE FDD and TD-LTE
• Scalable bandwidth up to 20 MHz
• Support for Multiple Input Multiple Output (MIMO) antenna technology
• New data and control channels
• New network and protocol architecture (two node, IP based)

LTE (3GPP Release 8) supports theoretical peak data rates of 300Mbps in downlink and 75Mbps in uplink direction. The first commercial network was launched in Sweden in December 2009 whereas meanwhile LTE has become the fastest growing mobile communication technology ever. Commercially available end user devices support max. 100Mbps (DL) / 50Mbps(UL). Please note that achievable data rates in real life networks varies depending on e.g. network load and propagation conditions and is generally significantly lower than the maximum rates achieved in test lab environment.

LTE-Advanced- In order to make LTE a true 4th generation (4G) technology, it was enhanced to meet the IMT-Advanced requirements issued by the International Telecommunication Union (ITU). The necessary improvements are specified in 3GPP Release 10 and also known as LTE-Advanced. IMT-conformant systems will be candidates for future spectrum bands that are still to be identified, which is another major reason for aligning LTE-Advanced with the call for IMT-Advanced technologies. This ensures that today’s deployed LTE mobile networks provide an evolutionary path towards many years of commercial operation. LTE-Advanced further increases peak data rates towards 1 Gbit/s in the downlink and 500 Mbit/s in the uplink.

The technology components of LTE-Advanced are:

• Carrier aggregation
• MIMO extension (up to DL: 8x8; up to UL: 4x4)
• Uplink access enhancements (clustered SC-FDMA and simultaneous data and control information (PUSCH and PUCCH) transmission
• Improving cell edge performance (enhanced inter-cell interference coordination (eICIC), relaying)

4. In the course several indoor distribution method are introduced. For each distribution method, what do you think the most suitable circumstance is? And state the reason.

LTE has been defined to accommodate both paired spectrum for Frequency Division Duplex, FDD and unpaired spectrum for Time Division Duplex, TDD operation. It is anticipated that both LTE TDD and LTE FDD will be widely deployed as each form of the LTE standard has its own advantages and disadvantages and decisions can be made about which format to adopt dependent upon the particular application.

LTE FDD using the paired spectrum is anticipated to form the migration path for the current 3G services being used around the globe, most of which use FDD paired spectrum. However there has been an additional emphasis on including TDD LTE using unpaired spectrum. TDD LTE which is also known as TD-LTE is seen as providing the evolution or upgrade path for TD-SCDMA.

In view of the increased level of importance being placed upon LTE TDD or TD-LTE, it is planned that user equipments will be designed to accommodate both FDD and TDD modes. With TDD having an increased level of importance placed upon it, it means that TDD operations will be able to benefit from the economies of scale that were previously only open to FDD operations.

Duplex schemes

It is essential that any cellular communications system must be able to transmit in both directions simultaneously. This enables conversations to be made, with either end being able to talk and listen as required. Additionally when exchanging data it is necessary to be able to undertake virtually simultaneous or completely simultaneous communications in both directions.

It is necessary to be able to specify the different direction of transmission so that it is possible to easily identify in which direction the transmission is being made. There are a variety of differences between the two links ranging from the amount of data carried to the transmission format, and the channels implemented. The two links are defined:

• Uplink:   the transmission from the UE or user equipment to the eNodeB or base station.
• Downlink   the transmission from the eNodeB or base station to the UE or user equipment.

In order to be able to be able to transmit in both directions, a user equipment or base station must have a duplex scheme. There are two forms of duplex that are commonly used, namely FDD, frequency division duplex and TDD time division duplex..

Note on TDD and FDD duplex schemes:

In order for radio communications systems to be able to communicate in both directions it is necessary to have what is termed a duplex scheme. A duplex scheme provides a way of organizing the transmitter and receiver so that they can transmit and receive. There are several methods that can be adopted. For applications including wireless and cellular telecommunications, where it is required that the transmitter and receiver are able to operate simultaneously, two schemes are in use. One known as FDD or frequency division duplex uses two channels, one for transmit and the other for receiver. Another scheme known as TDD, time division duplex uses one frequency, but allocates different time slots for transmission and reception.

Both FDD and TDD have their own advantages and disadvantages. Accordingly they may be used for different applications, or where the bias of the communications is different.

Advantages / disadvantages of LTE TDD and LTE FDD for cellular communications

There are a number of the advantages and disadvantages of TDD and FDD that are of particular interest to mobile or cellular telecommunications operators. These are naturally reflected into LTE.

Comparison of TDD LTE and FDD LTE Duplex Formats
Parameter	LTE-TDD	LTE-FDD
Paired spectrum	Does not require paired spectrum as both transmit and receive occur on the same channel	Requires paired spectrum with sufficient frequency separation to allow simultaneous transmission and reception
Hardware cost	Lower cost as no diplexer is needed to isolate the transmitter and receiver. As cost of the UEs is of major importance because of the vast numbers that are produced, this is a key aspect.	Diplexer is needed and cost is higher.
Channel reciprocity	Channel propagation is the same in both directions which enables transmit and receive to use on set of parameters	Channel characteristics different in both directions as a result of the use of different frequencies
UL / DL asymmetry	It is possible to dynamically change the UL and DL capacity ratio to match demand	UL / DL capacity determined by frequency allocation set out by the regulatory authorities. It is therefore not possible to make dynamic changes to match capacity. Regulatory changes would normally be required and capacity is normally allocated so that it is the same in either direction.
Guard period / guard band	Guard period required to ensure uplink and downlink transmissions do not clash. Large guard period will limit capacity. Larger guard period normally required if distances are increased to accommodate larger propagation times.	Guard band required to provide sufficient isolation between uplink and downlink. Large guard band does not impact capacity.
Discontinuous transmission	Discontinuous transmission is required to allow both uplink and downlink transmissions. This can degrade the performance of the RF power amplifier in the transmitter.	Continuous transmission is required.
Cross slot interference	Base stations need to be synchronised with respect to the uplink and downlink transmission times. If neighbouring base stations use different uplink and downlink assignments and share the same channel, then interference may occur between cells.	Not applicable

LTE TDD / TD-LTE and TD-SCDMA

Apart from the technical reasons and advantages for using LTE TDD / TD-LTE, there are market drivers as well. With TD-SCDMA now well established in China, there needs to be a 3.9G and later a 4G successor to the technology. With unpaired spectrum allocated for TD-SCDMA as well as UMTS TDD, it is natural to see many operators wanting an upgrade path for their technologies to benefit from the vastly increased speeds and improved facilities of LTE. Accordingly there is a considerable interest in the development of LTE TDD, which is also known in China as TD-LTE.

With the considerable interest from the supporters of TD-SCDMA, a number of features to make the mode of operation of TD-LTE more of an upgrade path for TD-SCDMA have been incorporated. One example of this is the subframe structure that has been adopted within LTE TDD / TD-LTE.

While both LTE TDD (TD-LTE) and LTE FDD will be widely used, it is anticipated that LTE FDD will be the more widespread, although LTE TDD has a number of significant advantages, especially in terms of higher spectrum efficiency that can be used by many operators. It is also anticipated that phones will be able to operate using either the LTE FDD or LTE-TDD (TD-LTE) modes. In this way the LTE UEs or user equipments will be dual standard phones, and able to operate in countries regardless of the flavour of LTE that is used - the main problem will then be the frequency bands that the phone can cover.

5. Conformance testing is most-likely to be adopted to ensure the terminal’s functionality and performance. Why do we need Conformance Testing

Conformance testing, also known as compliance testing, we need this methodology to be used in engineering to ensure that a product, process, computer program or system meets a defined set of standards. These standards are commonly defined by large, independent entities such as the Institute of Electrical and Electronics Engineers (IEEE), the World Wide Web Consortium (W3C) or the European Telecommunications Standards Institute (ETSI). Thus we can say conformance testing is most-likely to be adopted to ensure the terminal's functionality and performance.

Conformance testing can be carried out by private companies that specialize in that service. In some instances the vendor maintains an in-house department for conducting conformance tests prior to the initial release of a product or upgrade. In the software industry, once the set of tests has been completed and a program has been found to comply with all the applicable standards, that program can be advertised as having been certified by the organization that defined the standards and the corporation or organization that conducted the tests.