The London hard fork is a planned upgrade for the Ethereum blockchain, scheduled to occur around July 2021. This upgrade introduces several key improvements and changes to the Ethereum network, with the primary goals of enhancing user experience, improving transaction efficiency, and preparing the platform for future upgrades.

Here are the main features and changes expected with the London hard fork:

1. EIP-1559 (Ethereum Improvement Proposal 1559):
Fee Structure Change: EIP-1559 proposes a new fee structure for Ethereum transactions. Currently, users submit bids (gas fees) to have their transactions processed by miners. With EIP-1559, the fee mechanism will be replaced by a base fee that adjusts dynamically based on network demand. Users will include a tip to incentivize miners to prioritize their transactions. This aims to make gas fees more predictable and reduce volatility.

Burn Mechanism: Under EIP-1559, part of the base fee will be burned (destroyed) rather than paid to miners. This could result in Ethereum becoming a deflationary asset, where the total supply decreases over time if the burned fees exceed new issuance (block rewards).

2. Other Improvements:
Difficulty Bomb Delay: The difficulty bomb, also known as the "Ice Age," is a mechanism to gradually increase the difficulty of mining Ethereum, pushing the network towards the adoption of Ethereum 2.0 (proof-of-stake). The London hard fork will delay the difficulty bomb for approximately 12 to 24 months, giving more time for Ethereum 2.0 development and implementation.

Minor Adjustments: The upgrade includes minor technical improvements and changes to optimize Ethereum’s performance and prepare the network for future upgrades, such as Ethereum 2.0.

Potential Impact:

- **Transaction Fees**: Users and developers expect more predictable and stable transaction fees, potentially lowering costs for users during times of high network congestion.

Economic Changes: The burning of transaction fees could lead to Ethereum becoming a more scarce asset over time, potentially affecting its value and economic dynamics.

Network Performance: Improved efficiency and reduced congestion could lead to better user experience and encourage more decentralized applications (dApps) to be built on Ethereum.

Overall, the London hard fork represents a significant upgrade for Ethereum, addressing pressing issues like transaction fees and network scalability while preparing the platform for future developments such as Ethereum 2.0's transition to proof-of-stake.