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.
