Wireless Connections Exam Questions

• B Latency (1)
• The only correct answer is B. The correct answer is latency, the delay between a signal being sent and the reply being received.
• A is not correct because bandwidth is the maximum amount of data that can be transferred in a given time
• C is not correct because range is the maximum distance a wireless signal can reach
• D is not correct because speed is the rate at which data is transmitted once it is being sent, not the delay before a reply is received

• A Bandwidth is shared between the devices (1)
• The only correct answer is A. The correct answer is that bandwidth is shared between the devices.
• B is not correct because range is the distance a wireless signal can reach, which does not increase when more devices are added
• C is not correct because latency is the delay between a signal being sent and received, which is not removed by adding more devices
• D is not correct because speed is the rate at which data is transferred, which does not increase for each device when more devices are added

• C Range (1)
• The only correct answer is C. The correct answer is range, the distance a wireless signal can reach.
• A is not correct because bandwidth is the maximum capacity of a channel, not how far a signal can reach
• B is not correct because latency is the delay between sending and receiving data, not how far a signal can reach
• D is not correct because speed is how quickly data is transmitted, not how far a signal can reach

• B Higher data transfer speed (1)
• The only correct answer is B. The correct answer is higher data transfer speed.
• A is not correct because the 2.4 GHz band has the greater range
• C is not correct because the 2.4 GHz band passes through walls more easily
• D is not correct because the 5 GHz band does not use less bandwidth

Award one mark for:

• It is shared between more devices, so each device gets less (bandwidth) (1)

Allow 'the bandwidth is divided/split between the devices'.

Allow 'there is less bandwidth for each device'.

Do not accept 'the speed decreases' / 'the connection slows down' on its own.

Do not accept 'the bandwidth decreases' unless it refers to the bandwidth available to each device.

Do not accept 'the bandwidth increases'.

Award one mark for each of the following up to a maximum of two marks:

• A delay/time/lag (1)
• Between a signal/request being sent and a response/data being received (1)

Allow 'the time taken for data to travel from source to destination' for both marks.

Do not accept 'the speed at which data travels' / 'bandwidth' / 'the amount of data sent per second'.

Award one mark for any of the following up to a maximum of two marks:

• Interference from other electrical/electronic devices (1)
• Walls/obstacles block or weaken the signal (1)
• The signal gets weaker the further a device is from the access point (1)
• Other devices/networks use the same wireless channel/frequency (1)
• A wireless channel has less bandwidth than a wired connection (1)

Do not accept 'higher latency', because latency is a delay and does not reduce the speed at which data is transferred.

Do not accept 'wireless is slower' / 'wired is faster' without a reason.

Do not accept 'radio waves are slower than signals in a cable' as they travel at the same speed.

Award one mark for any of the following up to a maximum of two marks:

• Walls/obstacles between the device and the access point (1)
• Interference from other electrical devices/other devices/other wireless networks (1)
• Distance from the access point (1)
• Using a higher frequency band (e.g. 5GHz) (1)
• Low transmit power of the access point/device (1)

Allow thick walls/furniture for walls/obstacles

Do not accept using more bandwidth

Do not accept a weaker signal without a stated cause

Award up to two marks for a linked description such as:

• The further a device is from the wireless access point (1) the weaker the signal becomes (1)
• A device outside the range of an access point (1) cannot connect to the network / loses its connection (1)
• Walls and other obstacles reduce the range of the signal (1) so some areas of a building have a poor or no connection (1)
• A wireless network with a greater range (1) allows devices to connect from further away (1)

Do not accept responses that only state that range is measured in metres or give a definition of range, as these do not describe an effect on performance.

Do not accept responses about the number of devices or interference unless they are linked to range.

Award up to two marks for a linked description such as:

• Other electrical/radio devices nearby (1) interfere with the wireless signal so data is corrupted (1)
• Interference corrupts data (1) so the data has to be resent, which increases latency/slows the transfer (1)
• Interference reduces the strength of the signal received (1) which lowers the data transfer rate the connection can support (1)
• Interference makes the connection drop (1) so data transfer stops/devices have to reconnect (1)

Do not accept responses that only name a device (microwave, phone) without saying how it affects the network.

Do not accept responses that only state the network becomes slower without saying what causes the interference or how it affects the data.

Do not accept responses about wired connections or cables.

Award up to two marks for a linked description such as:

• The bandwidth/capacity of the access point is shared between all the connected devices (1) so each device gets less bandwidth as more devices connect, which reduces the speed of data transfer (1)
• The devices have to take turns to transmit (contention) (1) so each device waits longer before it can send data, which increases latency (1)
• The access point can only support a maximum number of connections (1) so once this limit is reached, further devices cannot connect to the network (1)

Allow 'contention' as an alternative to devices having to take turns to transmit.

Allow 'the network becomes slower' as the second mark only where it is linked to shared bandwidth, to devices taking turns to transmit or to the maximum number of connections.

Do not accept a response that only states the network becomes slower, or that there are more devices/more traffic, without saying how this affects performance.

Do not accept responses about range or interference unless they are linked to the number of connected devices.

Award up to two marks for a linked description such as:

• Interference from other devices corrupts the wireless signal (1) so the data has to be resent, which increases the delay (1)
• Devices on a wireless network take turns to use the same channel/frequency (1) so a device may have to wait for the channel to be free before it can transmit, which adds to the delay (1)
• Data on a wireless connection must pass through the access point to reach the wired network (1) so the extra processing/conversion at the access point adds a delay (1)

Do not accept responses that only state that a wireless connection is slower/less reliable than a wired connection, without explaining how this adds latency.

Do not accept 'data is sent through the air' on its own, as this does not explain why latency is higher.

Do not accept responses about bandwidth or speed on their own.

Award up to two marks for a linked explanation such as:

• Devices near the edge/limit of the range receive a weaker signal/lower signal strength (1) so data is transferred more slowly/the connection speed/bandwidth is lower (1)
• Devices near the edge/limit of the range receive a weaker signal/lower signal strength (1) so latency increases (1)
• Devices outside the range cannot connect to the access point (1) so users in that area cannot use the network/access its resources (1)
• A device that moves out of range loses its connection (1) so the user's work is interrupted until it is back in range (1)

For both marks, the expansion must follow/associate with the statement.

For the second mark, the reason must state the effect on the user/network (e.g. cannot use the network/access resources, slower speed, higher latency), not just repeat that the device is out of range.

Do not accept a definition of range on its own (e.g. 'range is how far the signal reaches') without an effect on performance.

Do not accept 'a larger range means more devices can connect' (range is not about the number of devices/capacity).

Do not accept range confused with bandwidth/speed, e.g. 'range is the maximum amount of data that can be transferred'.

Award up to two marks for a linked explanation such as:

• Wireless signals can be blocked or absorbed by walls (1) so the data must be re-sent, which adds delay (1)
• A device further from the access point has a weaker signal (1) so data must be re-sent/transmitted at a lower rate, adding delay (1)
• Devices on a wireless network share a channel (1) so a device must wait its turn to transmit, which adds delay (1)
• Interference from other devices affects the radio signal (1) so data must be re-sent, adding delay (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'waiting to send' or 'collisions' as the delay caused by devices sharing a channel.

Do not accept 'wireless is slower than wired' on its own, as this repeats the question.

Do not accept a reason that only affects download speed/bandwidth (e.g. 'files take longer to download') without a link to delay.

Award up to two marks for a linked explanation such as:

• (All) devices share the bandwidth of the access point (1) so each device gets a smaller share, which reduces its speed/slows down transfers (1)
• Bandwidth is the maximum amount of data that can be transferred at one time (1) so when devices send more data than this, the data must wait/queue, which slows down transfers (1)
• (Many) devices send data at the same time (1) so the devices take turns, which reduces the amount of data each one can send/the speed each device gets (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'connection speed'/'download speed' for speed.

Do not accept 'the signal is shared' without saying that this reduces the bandwidth/data each device can send.

Do not accept the idea that adding devices increases the bandwidth.

Award up to two marks for a linked explanation such as:

• The speed of data transfer is reduced/is slower (1) because interference corrupts the radio signal, so data/packets are lost and have to be resent/retransmitted (1)
• The network speed is lower (1) because there is more noise on the wireless signal, so data is sent at a lower transmission rate (1)
• The throughput of the wireless network is reduced (1) because time is used resending corrupted data/packets instead of sending new data (1)

For both marks, the expansion must follow/associate with the statement.

Award 1 mark for a statement that the speed/transfer rate is reduced (e.g. slower, takes longer), even if no reason is given.

Do not accept 'interference damages/corrupts the radio signal' or 'the signal is weaker' on its own without a link to the speed.

Do not accept 'data is lost' on its own without saying how this reduces the speed.

Do not accept 'interference increases the bandwidth' or 'interference makes the signal stronger'.

Indicative content

Range

• Range is the maximum distance a device can be from an access point and still send and receive data.
• A student who moves beyond the range of an access point cannot connect to the school network at all.
• As a device gets close to the edge of the range the signal becomes weaker, so the connection becomes slower and less reliable.

Building features

• The thick walls and floors of the new building absorb radio waves, so the signal does not travel as far and some rooms will have a weak signal.
• Interference from other wireless networks and from electrical equipment in the building reduces the distance over which the signal can be used.
• A signal using the 2.4 GHz band travels further through walls than one using the 5 GHz band, so 2.4 GHz gives coverage over a greater range.
• An access point on the ground floor is likely to be out of range of students on the upper floor, so they will not be able to connect.

Improving the connection

• The school should install more access points so that every student is always within range of one.
• The access points should be positioned so there are no blind spots, with at least one access point on each floor.
• Each access point should be connected to the wired network with a cable, so the wireless coverage it provides is reliable.
• The school could use the 2.4 GHz band in rooms where the signal has to pass through several walls, to reach further.

Levels

• Level 0 (0 marks): No rewardable content.
• Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
• Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
• Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must cover the effect of the building on range and how coverage across the school could be improved.

Answers that confuse range with the speed or bandwidth of the connection are limited to Level 1.

Indicative content

Bandwidth

• Bandwidth is the maximum amount of data that can be transmitted over the connection in a given time.
• Do not accept 'the number of devices connected' or 'the speed of the internet' as a definition of bandwidth.
• The bandwidth of the family's wireless connection is shared between all four people's devices, so the more of them that are in use in the evening, the smaller the share each one gets.
• Streaming a film sends a large amount of data continuously, so it takes a large share of the bandwidth and leaves less for the online games and video calls.

Effect of the devices

• When all four devices are connected in the evening, each one can only receive data at a fraction of the total bandwidth, so the internet feels slower on every device in the house.
• The wireless devices in the home have to take turns to transmit on the same channel, so the more devices the family connects, the longer each one waits before it can send or receive.
• Interference from neighbouring wireless networks, and the walls between the router and the devices, reduces the amount of data that arrives correctly, so the data is resent and the connection slows down.
• A device used far from the router, such as in an upstairs bedroom, gets a weak signal, so its data has to be resent and its connection is slower.
• If one person downloads a large file or updates a games console, that uses most of the bandwidth and slows down everyone else in the house.

Improving performance

• Devices that do not move, such as the smart TV or a games console, could be connected to the router with an Ethernet cable, so the wireless bandwidth is left for the devices that need it.
• The family could move the router to the middle of the house and away from walls, so every device gets a stronger signal and fewer resends are needed.
• The family could use the 5 GHz band, which has more channels and higher data rates than 2.4 GHz, although it does not pass through walls as well.
• The family could ask their provider for a connection with a higher bandwidth, so there is more capacity for the four people's devices to share in the evening.

Levels

• Level 0 (0 marks): No rewardable content.
• Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
• Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
• Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must explain how the bandwidth is shared between the four people's devices and must give at least one reason, such as taking turns on the channel, interference or a weak signal, why the wireless connection is slow in the evening.

Answers that only state that more devices make the connection slower, without giving a reason, are limited to Level 1.