Understand how the characteristics of wired and wireless connectivity impact on performance (speed, range, latency, bandwidth), that network speeds are measured in bits per second, and construct expressions involving file size, transmission rate and time.

What this dot point is asking

Edexcel wants you to compare wired and wireless connections by their effect on performance (speed, range, latency, bandwidth), to know that network speed is measured in bits per second, and to calculate using file size, transmission rate and time.

Key performance terms

These terms are often confused, so anchor each: bandwidth is the capacity (how much per second the link can carry), latency is the delay (how long before data arrives), speed is the actual rate achieved, and range is the distance covered. A connection can have high bandwidth but also high latency, so both matter for performance.

Wired versus wireless

The trade-off is performance versus convenience. A wired desktop gets the most consistent, fastest, lowest-latency connection, which is why gaming PCs and servers are often wired. Wireless lets phones, laptops and tablets connect anywhere in range without cabling, which is why it dominates for mobile devices, at the cost of a signal that weakens with distance and is disturbed by interference and walls, and that slows when many devices share it.

Network speed units

The bits-versus-bytes point is the single biggest source of calculation errors. A "50 Mbps" connection moves 50 million bits per second, while a file size is often quoted in bytes. Always make the file size and the rate use the same unit (both bits or both bytes) before dividing.

Calculating transmission time

Bringing performance and calculations together

When Edexcel asks why one connection performs better, answer in terms of bandwidth, latency, reliability and range, contrasting wired and wireless. When it asks for a transmission time, use $\text{time} = \text{size} \div \text{rate}$ with matching units. The two ideas connect: a higher-bandwidth (often wired) connection transfers a given file in less time, which is exactly what the calculation shows.

Try this

Q1. State the unit in which network transmission speed is measured. [1 mark]

• Cue. Bits per second (for example megabits per second).

Q2. A 16 megabit file is sent at 4 megabits per second. Calculate the transmission time. [1 mark]

• Cue. $16 \div 4 = 4$ seconds.